diff --git a/compiler/packages/babel-plugin-react-compiler/src/HIR/ObjectShape.ts b/compiler/packages/babel-plugin-react-compiler/src/HIR/ObjectShape.ts
index 9554878578ca0..04f85e496453a 100644
--- a/compiler/packages/babel-plugin-react-compiler/src/HIR/ObjectShape.ts
+++ b/compiler/packages/babel-plugin-react-compiler/src/HIR/ObjectShape.ts
@@ -317,6 +317,23 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
       mutableOnlyIfOperandsAreMutable: true,
     }),
   ],
+  [
+    'flatMap',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.ConditionallyMutate,
+      returnType: {kind: 'Object', shapeId: BuiltInArrayId},
+      /*
+       * callee is ConditionallyMutate because items of the array
+       * flow into the lambda and may be mutated there, even though
+       * the array object itself is not modified
+       */
+      calleeEffect: Effect.ConditionallyMutate,
+      returnValueKind: ValueKind.Mutable,
+      noAlias: true,
+      mutableOnlyIfOperandsAreMutable: true,
+    }),
+  ],
   [
     'filter',
     addFunction(BUILTIN_SHAPES, [], {
@@ -534,6 +551,17 @@ addObject(BUILTIN_SHAPES, BuiltInMixedReadonlyId, [
       noAlias: true,
     }),
   ],
+  [
+    'flatMap',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Object', shapeId: BuiltInArrayId},
+      calleeEffect: Effect.ConditionallyMutate,
+      returnValueKind: ValueKind.Mutable,
+      noAlias: true,
+    }),
+  ],
   [
     'filter',
     addFunction(BUILTIN_SHAPES, [], {