diff --git a/java/ql/lib/change-notes/2026-11-12-mono-api.md b/java/ql/lib/change-notes/2026-11-12-mono-api.md
new file mode 100644
index 000000000000..a7a1ba32af28
--- /dev/null
+++ b/java/ql/lib/change-notes/2026-11-12-mono-api.md
@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Added taint flow model for `reactor.core.publisher.Mono<T>`.
\ No newline at end of file
diff --git a/java/ql/lib/ext/reactor.core.publisher.model.json b/java/ql/lib/ext/reactor.core.publisher.model.json
new file mode 100644
index 000000000000..e5de0a105b20
--- /dev/null
+++ b/java/ql/lib/ext/reactor.core.publisher.model.json
@@ -0,0 +1,21 @@
+{
+  "extensions": [
+    {
+      "addsTo": {
+        "pack": "codeql/java-all",
+        "extensible": "summaryModel"
+      },
+      "data": [
+        ["reactor.core.publisher", "Mono", true, "justOrEmpty", "(Object)", "", "Argument[0]", "ReturnValue.Element", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "justOrEmpty", "(Optional)", "", "Argument[0].Element", "ReturnValue.Element", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "just", "", "", "Argument[0]", "ReturnValue.Element", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "flatMap", "", "", "Argument[this].Element", "Argument[0].Parameter[0]", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "flatMap", "", "", "Argument[0].ReturnValue.Element", "ReturnValue.Element", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "map", "", "", "Argument[this].Element", "Argument[0].Parameter[0]", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "map", "", "", "Argument[0].ReturnValue", "ReturnValue.Element", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "mapNotNull", "", "", "Argument[this].Element", "Argument[0].Parameter[0]", "value", "manual"],
+        ["reactor.core.publisher", "Mono", true, "mapNotNull", "", "", "Argument[0].ReturnValue", "ReturnValue.Element", "value", "manual"]
+      ]
+    }
+  ]
+}
\ No newline at end of file
diff --git a/java/ql/test/library-tests/frameworks/reactor-core/Test.java b/java/ql/test/library-tests/frameworks/reactor-core/Test.java
new file mode 100644
index 000000000000..4ba9e5dc0cd1
--- /dev/null
+++ b/java/ql/test/library-tests/frameworks/reactor-core/Test.java
@@ -0,0 +1,136 @@
+import java.util.Optional;
+import reactor.core.publisher.Mono;
+
+public class Test {
+
+    void sink(Object o) {}
+
+    String taint() {
+        return null;
+    }
+
+    void testJust() {
+        Mono<String> unsafe = Mono.just(taint());
+        unsafe.map(value -> {
+            sink(value); // $ hasValueFlow
+            return value;
+        });
+        Mono<String> safe = Mono.just("safe");
+        safe.map(value -> {
+            sink(value); // no taint flow
+            return value;
+        });
+    }
+
+    void testJustOrEmpty() {
+        Mono<String> unsafe = Mono.justOrEmpty(taint());
+        unsafe.map(value -> {
+            sink(value); // $ hasValueFlow
+            return value;
+        });
+        Mono<String> safe = Mono.justOrEmpty("safe");
+        safe.map(value -> {
+            sink(value); // no taint flow
+            return value;
+        });
+    }
+
+    void testJustOrEmptyOptional() {
+        Mono<String> unsafe = Mono.justOrEmpty(Optional.of(taint()));
+        unsafe.map(value -> {
+            sink(value); // $ hasValueFlow
+            return value;
+        });
+        Mono<String> safe = Mono.justOrEmpty(Optional.of("safe"));
+        safe.map(value -> {
+            sink(value); // no taint flow
+            return value;
+        });
+        Mono<String> empty = Mono.justOrEmpty(Optional.<String>empty());
+        empty.map(value -> {
+            sink(value); // no taint flow
+            return value;
+        });
+    }
+
+    void testFlatMap() {
+        Mono.just(taint()).flatMap(value -> {
+            sink(value); // $ hasValueFlow
+            return Mono.just("safe");
+        });
+        Mono.just("safe").flatMap(value -> {
+            sink(value); // no taint flow
+            return Mono.just("safe");
+        });
+    }
+
+    void testMap() {
+        Mono.just(taint()).map(value -> {
+            sink(value); // $ hasValueFlow
+            return "safe";
+        });
+        Mono.just("safe").map(value -> {
+            sink(value); // no taint flow
+            return "safe";
+        });
+    }
+
+    void testMapNotNull() {
+        Mono.just(taint()).mapNotNull(value -> {
+            sink(value); // $ hasValueFlow
+            return "safe";
+        });
+        Mono.just("safe").mapNotNull(value -> {
+            sink(value); // no taint flow
+            return "safe";
+        });
+    }
+
+    void testFlatMapResult() {
+        Mono.just("safe").flatMap(value -> Mono.just(taint())).map(value -> {
+            sink(value); // $ hasValueFlow
+            return value;
+        });
+        Mono.just(taint()).flatMap(value -> Mono.just("safe")).map(value -> {
+            sink(value); // no taint flow
+            return value;
+        });
+    }
+
+    void testMapResult() {
+        Mono.just("safe").map(value -> taint()).map(value -> {
+            sink(value); // $ hasValueFlow
+            return value;
+        });
+        Mono.just(taint()).map(value -> "safe").map(value -> {
+            sink(value); // no taint flow
+            return value;
+        });
+    }
+
+    void testMapNotNullResult() {
+        Mono.just("safe").mapNotNull(value -> taint()).map(value -> {
+            sink(value); // $ hasValueFlow
+            return value;
+        });
+        Mono.just(taint()).mapNotNull(value -> "safe").map(value -> {
+            sink(value); // no taint flow
+            return value;
+        });
+    }
+
+    void testNestedValues() {
+        Mono.just(Optional.of(taint())).flatMap(value -> {
+            sink(value.get()); // $ hasValueFlow
+            return Mono.just("safe");
+        });
+        Mono.just(Optional.of(taint())).map(value -> {
+            sink(value.get()); // $ hasValueFlow
+            return "safe";
+        });
+        Mono.just(Optional.of(taint())).mapNotNull(value -> {
+            sink(value.get()); // $ hasValueFlow
+            return "safe";
+        });
+    }
+}
\ No newline at end of file
diff --git a/java/ql/test/library-tests/frameworks/reactor-core/options b/java/ql/test/library-tests/frameworks/reactor-core/options
new file mode 100644
index 000000000000..b5399283a6d2
--- /dev/null
+++ b/java/ql/test/library-tests/frameworks/reactor-core/options
@@ -0,0 +1 @@
+//semmle-extractor-options: --javac-args -cp ${testdir}/../../../stubs/reactor-core
diff --git a/java/ql/test/library-tests/frameworks/reactor-core/test.expected b/java/ql/test/library-tests/frameworks/reactor-core/test.expected
new file mode 100644
index 000000000000..b42c7c901860
--- /dev/null
+++ b/java/ql/test/library-tests/frameworks/reactor-core/test.expected
@@ -0,0 +1,122 @@
+models
+| 1 | Summary: java.util; Optional; false; get; ; ; Argument[this].Element; ReturnValue; value; manual |
+| 2 | Summary: java.util; Optional; false; of; ; ; Argument[0]; ReturnValue.Element; value; manual |
+| 3 | Summary: reactor.core.publisher; Mono; true; flatMap; ; ; Argument[0].ReturnValue.Element; ReturnValue.Element; value; manual |
+| 4 | Summary: reactor.core.publisher; Mono; true; flatMap; ; ; Argument[this].Element; Argument[0].Parameter[0]; value; manual |
+| 5 | Summary: reactor.core.publisher; Mono; true; just; ; ; Argument[0]; ReturnValue.Element; value; manual |
+| 6 | Summary: reactor.core.publisher; Mono; true; justOrEmpty; (Object); ; Argument[0]; ReturnValue.Element; value; manual |
+| 7 | Summary: reactor.core.publisher; Mono; true; justOrEmpty; (Optional); ; Argument[0].Element; ReturnValue.Element; value; manual |
+| 8 | Summary: reactor.core.publisher; Mono; true; map; ; ; Argument[0].ReturnValue; ReturnValue.Element; value; manual |
+| 9 | Summary: reactor.core.publisher; Mono; true; map; ; ; Argument[this].Element; Argument[0].Parameter[0]; value; manual |
+| 10 | Summary: reactor.core.publisher; Mono; true; mapNotNull; ; ; Argument[0].ReturnValue; ReturnValue.Element; value; manual |
+| 11 | Summary: reactor.core.publisher; Mono; true; mapNotNull; ; ; Argument[this].Element; Argument[0].Parameter[0]; value; manual |
+edges
+| Test.java:13:31:13:48 | just(...) : Mono [<element>] : String | Test.java:14:9:14:14 | unsafe : Mono [<element>] : String | provenance |  |
+| Test.java:13:41:13:47 | taint(...) : String | Test.java:13:31:13:48 | just(...) : Mono [<element>] : String | provenance | MaD:5 |
+| Test.java:14:9:14:14 | unsafe : Mono [<element>] : String | Test.java:14:20:14:24 | value : String | provenance | MaD:9 |
+| Test.java:14:20:14:24 | value : String | Test.java:15:18:15:22 | value | provenance |  |
+| Test.java:26:31:26:55 | justOrEmpty(...) : Mono [<element>] : String | Test.java:27:9:27:14 | unsafe : Mono [<element>] : String | provenance |  |
+| Test.java:26:48:26:54 | taint(...) : String | Test.java:26:31:26:55 | justOrEmpty(...) : Mono [<element>] : String | provenance | MaD:6 |
+| Test.java:27:9:27:14 | unsafe : Mono [<element>] : String | Test.java:27:20:27:24 | value : String | provenance | MaD:9 |
+| Test.java:27:20:27:24 | value : String | Test.java:28:18:28:22 | value | provenance |  |
+| Test.java:39:31:39:68 | justOrEmpty(...) : Mono [<element>] : String | Test.java:40:9:40:14 | unsafe : Mono [<element>] : String | provenance |  |
+| Test.java:39:48:39:67 | of(...) : Optional [<element>] : String | Test.java:39:31:39:68 | justOrEmpty(...) : Mono [<element>] : String | provenance | MaD:7 |
+| Test.java:39:60:39:66 | taint(...) : String | Test.java:39:48:39:67 | of(...) : Optional [<element>] : String | provenance | MaD:2 |
+| Test.java:40:9:40:14 | unsafe : Mono [<element>] : String | Test.java:40:20:40:24 | value : String | provenance | MaD:9 |
+| Test.java:40:20:40:24 | value : String | Test.java:41:18:41:22 | value | provenance |  |
+| Test.java:57:9:57:26 | just(...) : Mono [<element>] : String | Test.java:57:36:57:40 | value : String | provenance | MaD:4 |
+| Test.java:57:19:57:25 | taint(...) : String | Test.java:57:9:57:26 | just(...) : Mono [<element>] : String | provenance | MaD:5 |
+| Test.java:57:36:57:40 | value : String | Test.java:58:18:58:22 | value | provenance |  |
+| Test.java:68:9:68:26 | just(...) : Mono [<element>] : String | Test.java:68:32:68:36 | value : String | provenance | MaD:9 |
+| Test.java:68:19:68:25 | taint(...) : String | Test.java:68:9:68:26 | just(...) : Mono [<element>] : String | provenance | MaD:5 |
+| Test.java:68:32:68:36 | value : String | Test.java:69:18:69:22 | value | provenance |  |
+| Test.java:79:9:79:26 | just(...) : Mono [<element>] : String | Test.java:79:39:79:43 | value : String | provenance | MaD:11 |
+| Test.java:79:19:79:25 | taint(...) : String | Test.java:79:9:79:26 | just(...) : Mono [<element>] : String | provenance | MaD:5 |
+| Test.java:79:39:79:43 | value : String | Test.java:80:18:80:22 | value | provenance |  |
+| Test.java:90:9:90:62 | flatMap(...) : Mono [<element>] : String | Test.java:90:68:90:72 | value : String | provenance | MaD:9 |
+| Test.java:90:44:90:61 | just(...) : Mono [<element>] : String | Test.java:90:9:90:62 | flatMap(...) : Mono [<element>] : String | provenance | MaD:3 |
+| Test.java:90:54:90:60 | taint(...) : String | Test.java:90:44:90:61 | just(...) : Mono [<element>] : String | provenance | MaD:5 |
+| Test.java:90:68:90:72 | value : String | Test.java:91:18:91:22 | value | provenance |  |
+| Test.java:101:9:101:47 | map(...) : Mono [<element>] : String | Test.java:101:53:101:57 | value : String | provenance | MaD:9 |
+| Test.java:101:40:101:46 | taint(...) : String | Test.java:101:9:101:47 | map(...) : Mono [<element>] : String | provenance | MaD:8 |
+| Test.java:101:53:101:57 | value : String | Test.java:102:18:102:22 | value | provenance |  |
+| Test.java:112:9:112:54 | mapNotNull(...) : Mono [<element>] : String | Test.java:112:60:112:64 | value : String | provenance | MaD:9 |
+| Test.java:112:47:112:53 | taint(...) : String | Test.java:112:9:112:54 | mapNotNull(...) : Mono [<element>] : String | provenance | MaD:10 |
+| Test.java:112:60:112:64 | value : String | Test.java:113:18:113:22 | value | provenance |  |
+| Test.java:123:9:123:39 | just(...) : Mono [<element>, <element>] : String | Test.java:123:49:123:53 | value : Optional [<element>] : String | provenance | MaD:4 |
+| Test.java:123:19:123:38 | of(...) : Optional [<element>] : String | Test.java:123:9:123:39 | just(...) : Mono [<element>, <element>] : String | provenance | MaD:5 |
+| Test.java:123:31:123:37 | taint(...) : String | Test.java:123:19:123:38 | of(...) : Optional [<element>] : String | provenance | MaD:2 |
+| Test.java:123:49:123:53 | value : Optional [<element>] : String | Test.java:124:18:124:22 | value : Optional [<element>] : String | provenance |  |
+| Test.java:124:18:124:22 | value : Optional [<element>] : String | Test.java:124:18:124:28 | get(...) | provenance | MaD:1 |
+| Test.java:127:9:127:39 | just(...) : Mono [<element>, <element>] : String | Test.java:127:45:127:49 | value : Optional [<element>] : String | provenance | MaD:9 |
+| Test.java:127:19:127:38 | of(...) : Optional [<element>] : String | Test.java:127:9:127:39 | just(...) : Mono [<element>, <element>] : String | provenance | MaD:5 |
+| Test.java:127:31:127:37 | taint(...) : String | Test.java:127:19:127:38 | of(...) : Optional [<element>] : String | provenance | MaD:2 |
+| Test.java:127:45:127:49 | value : Optional [<element>] : String | Test.java:128:18:128:22 | value : Optional [<element>] : String | provenance |  |
+| Test.java:128:18:128:22 | value : Optional [<element>] : String | Test.java:128:18:128:28 | get(...) | provenance | MaD:1 |
+| Test.java:131:9:131:39 | just(...) : Mono [<element>, <element>] : String | Test.java:131:52:131:56 | value : Optional [<element>] : String | provenance | MaD:11 |
+| Test.java:131:19:131:38 | of(...) : Optional [<element>] : String | Test.java:131:9:131:39 | just(...) : Mono [<element>, <element>] : String | provenance | MaD:5 |
+| Test.java:131:31:131:37 | taint(...) : String | Test.java:131:19:131:38 | of(...) : Optional [<element>] : String | provenance | MaD:2 |
+| Test.java:131:52:131:56 | value : Optional [<element>] : String | Test.java:132:18:132:22 | value : Optional [<element>] : String | provenance |  |
+| Test.java:132:18:132:22 | value : Optional [<element>] : String | Test.java:132:18:132:28 | get(...) | provenance | MaD:1 |
+nodes
+| Test.java:13:31:13:48 | just(...) : Mono [<element>] : String | semmle.label | just(...) : Mono [<element>] : String |
+| Test.java:13:41:13:47 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:14:9:14:14 | unsafe : Mono [<element>] : String | semmle.label | unsafe : Mono [<element>] : String |
+| Test.java:14:20:14:24 | value : String | semmle.label | value : String |
+| Test.java:15:18:15:22 | value | semmle.label | value |
+| Test.java:26:31:26:55 | justOrEmpty(...) : Mono [<element>] : String | semmle.label | justOrEmpty(...) : Mono [<element>] : String |
+| Test.java:26:48:26:54 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:27:9:27:14 | unsafe : Mono [<element>] : String | semmle.label | unsafe : Mono [<element>] : String |
+| Test.java:27:20:27:24 | value : String | semmle.label | value : String |
+| Test.java:28:18:28:22 | value | semmle.label | value |
+| Test.java:39:31:39:68 | justOrEmpty(...) : Mono [<element>] : String | semmle.label | justOrEmpty(...) : Mono [<element>] : String |
+| Test.java:39:48:39:67 | of(...) : Optional [<element>] : String | semmle.label | of(...) : Optional [<element>] : String |
+| Test.java:39:60:39:66 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:40:9:40:14 | unsafe : Mono [<element>] : String | semmle.label | unsafe : Mono [<element>] : String |
+| Test.java:40:20:40:24 | value : String | semmle.label | value : String |
+| Test.java:41:18:41:22 | value | semmle.label | value |
+| Test.java:57:9:57:26 | just(...) : Mono [<element>] : String | semmle.label | just(...) : Mono [<element>] : String |
+| Test.java:57:19:57:25 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:57:36:57:40 | value : String | semmle.label | value : String |
+| Test.java:58:18:58:22 | value | semmle.label | value |
+| Test.java:68:9:68:26 | just(...) : Mono [<element>] : String | semmle.label | just(...) : Mono [<element>] : String |
+| Test.java:68:19:68:25 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:68:32:68:36 | value : String | semmle.label | value : String |
+| Test.java:69:18:69:22 | value | semmle.label | value |
+| Test.java:79:9:79:26 | just(...) : Mono [<element>] : String | semmle.label | just(...) : Mono [<element>] : String |
+| Test.java:79:19:79:25 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:79:39:79:43 | value : String | semmle.label | value : String |
+| Test.java:80:18:80:22 | value | semmle.label | value |
+| Test.java:90:9:90:62 | flatMap(...) : Mono [<element>] : String | semmle.label | flatMap(...) : Mono [<element>] : String |
+| Test.java:90:44:90:61 | just(...) : Mono [<element>] : String | semmle.label | just(...) : Mono [<element>] : String |
+| Test.java:90:54:90:60 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:90:68:90:72 | value : String | semmle.label | value : String |
+| Test.java:91:18:91:22 | value | semmle.label | value |
+| Test.java:101:9:101:47 | map(...) : Mono [<element>] : String | semmle.label | map(...) : Mono [<element>] : String |
+| Test.java:101:40:101:46 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:101:53:101:57 | value : String | semmle.label | value : String |
+| Test.java:102:18:102:22 | value | semmle.label | value |
+| Test.java:112:9:112:54 | mapNotNull(...) : Mono [<element>] : String | semmle.label | mapNotNull(...) : Mono [<element>] : String |
+| Test.java:112:47:112:53 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:112:60:112:64 | value : String | semmle.label | value : String |
+| Test.java:113:18:113:22 | value | semmle.label | value |
+| Test.java:123:9:123:39 | just(...) : Mono [<element>, <element>] : String | semmle.label | just(...) : Mono [<element>, <element>] : String |
+| Test.java:123:19:123:38 | of(...) : Optional [<element>] : String | semmle.label | of(...) : Optional [<element>] : String |
+| Test.java:123:31:123:37 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:123:49:123:53 | value : Optional [<element>] : String | semmle.label | value : Optional [<element>] : String |
+| Test.java:124:18:124:22 | value : Optional [<element>] : String | semmle.label | value : Optional [<element>] : String |
+| Test.java:124:18:124:28 | get(...) | semmle.label | get(...) |
+| Test.java:127:9:127:39 | just(...) : Mono [<element>, <element>] : String | semmle.label | just(...) : Mono [<element>, <element>] : String |
+| Test.java:127:19:127:38 | of(...) : Optional [<element>] : String | semmle.label | of(...) : Optional [<element>] : String |
+| Test.java:127:31:127:37 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:127:45:127:49 | value : Optional [<element>] : String | semmle.label | value : Optional [<element>] : String |
+| Test.java:128:18:128:22 | value : Optional [<element>] : String | semmle.label | value : Optional [<element>] : String |
+| Test.java:128:18:128:28 | get(...) | semmle.label | get(...) |
+| Test.java:131:9:131:39 | just(...) : Mono [<element>, <element>] : String | semmle.label | just(...) : Mono [<element>, <element>] : String |
+| Test.java:131:19:131:38 | of(...) : Optional [<element>] : String | semmle.label | of(...) : Optional [<element>] : String |
+| Test.java:131:31:131:37 | taint(...) : String | semmle.label | taint(...) : String |
+| Test.java:131:52:131:56 | value : Optional [<element>] : String | semmle.label | value : Optional [<element>] : String |
+| Test.java:132:18:132:22 | value : Optional [<element>] : String | semmle.label | value : Optional [<element>] : String |
+| Test.java:132:18:132:28 | get(...) | semmle.label | get(...) |
+subpaths
+testFailures
diff --git a/java/ql/test/library-tests/frameworks/reactor-core/test.ql b/java/ql/test/library-tests/frameworks/reactor-core/test.ql
new file mode 100644
index 000000000000..de0d4722737b
--- /dev/null
+++ b/java/ql/test/library-tests/frameworks/reactor-core/test.ql
@@ -0,0 +1,4 @@
+import java
+import utils.test.InlineFlowTest
+import DefaultFlowTest
+import TaintFlow::PathGraph
diff --git a/java/ql/test/stubs/reactor-core/LICENSE.txt b/java/ql/test/stubs/reactor-core/LICENSE.txt
new file mode 100644
index 000000000000..bfad273e3d9f
--- /dev/null
+++ b/java/ql/test/stubs/reactor-core/LICENSE.txt
@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        https://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
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\ No newline at end of file
diff --git a/java/ql/test/stubs/reactor-core/reactor/core/publisher/Mono.java b/java/ql/test/stubs/reactor-core/reactor/core/publisher/Mono.java
new file mode 100644
index 000000000000..dfd4890221e6
--- /dev/null
+++ b/java/ql/test/stubs/reactor-core/reactor/core/publisher/Mono.java
@@ -0,0 +1,30 @@
+package reactor.core.publisher;
+
+import java.util.Optional;
+import java.util.function.Function;
+
+public abstract class Mono<T> {
+    public static <T> Mono<T> just(T value) {
+        return null;
+    }
+
+    public static <T> Mono<T> justOrEmpty(T value) {
+        return null;
+    }
+
+    public static <T> Mono<T> justOrEmpty(Optional<? extends T> value) {
+        return null;
+    }
+
+    public final <R> Mono<R> flatMap(Function<? super T, ? extends Mono<? extends R>> mapper) {
+        return null;
+    }
+
+    public final <R> Mono<R> map(Function<? super T, ? extends R> mapper) {
+        return null;
+    }
+
+    public final <R> Mono<R> mapNotNull(Function<? super T, ? extends R> mapper) {
+        return null;
+    }
+}