diff --git a/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp b/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp
index c60901426521..b88b7a320ff6 100644
--- a/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp
+++ b/clang/lib/CIR/Lowering/ThroughMLIR/LowerCIRToMLIR.cpp
@@ -279,6 +279,18 @@ class CIRStoreOpLowering : public mlir::OpConversionPattern<cir::StoreOp> {
   }
 };
 
+class CIRACosOpLowering : public mlir::OpConversionPattern<cir::ACosOp> {
+public:
+  using OpConversionPattern<cir::ACosOp>::OpConversionPattern;
+
+  mlir::LogicalResult
+  matchAndRewrite(cir::ACosOp op, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    rewriter.replaceOpWithNewOp<mlir::math::AcosOp>(op, adaptor.getSrc());
+    return mlir::LogicalResult::success();
+  }
+};
+
 class CIRATanOpLowering : public mlir::OpConversionPattern<cir::ATanOp> {
 public:
   using OpConversionPattern<cir::ATanOp>::OpConversionPattern;
@@ -1383,7 +1395,7 @@ void populateCIRToMLIRConversionPatterns(mlir::RewritePatternSet &patterns,
            CIRBitClzOpLowering, CIRBitCtzOpLowering, CIRBitPopcountOpLowering,
            CIRBitClrsbOpLowering, CIRBitFfsOpLowering, CIRBitParityOpLowering,
            CIRIfOpLowering, CIRVectorCreateLowering, CIRVectorInsertLowering,
-           CIRVectorExtractLowering, CIRVectorCmpOpLowering>(
+           CIRVectorExtractLowering, CIRVectorCmpOpLowering, CIRACosOpLowering>(
           converter, patterns.getContext());
 }
 
diff --git a/clang/test/CIR/Lowering/ThroughMLIR/acos.cir b/clang/test/CIR/Lowering/ThroughMLIR/acos.cir
new file mode 100644
index 000000000000..f885c7adea7d
--- /dev/null
+++ b/clang/test/CIR/Lowering/ThroughMLIR/acos.cir
@@ -0,0 +1,30 @@
+// RUN: cir-opt %s -cir-to-mlir -o %t.mlir
+// RUN: FileCheck %s --input-file %t.mlir
+
+module {
+  cir.func @foo() {
+    %0 = cir.const #cir.fp<1.0> : !cir.float
+    %1 = cir.const #cir.fp<3.0> : !cir.long_double<!cir.f80>
+    %2 = cir.const #cir.fp<2.0> : !cir.double
+    %3 = cir.const #cir.fp<4.00> : !cir.long_double<!cir.double>
+    %4 = cir.acos %0 : !cir.float
+    %5 = cir.acos %1 : !cir.long_double<!cir.f80>
+    %6 = cir.acos %2 : !cir.double
+    %7 = cir.acos %3 : !cir.long_double<!cir.double>
+    cir.return
+  }
+}
+
+// CHECK:      module {
+// CHECK-NEXT:   func.func @foo() {
+// CHECK-NEXT:     %[[C0:.+]] = arith.constant 1.000000e+00 : f32
+// CHECK-NEXT:     %[[C1:.+]] = arith.constant 3.000000e+00 : f80
+// CHECK-NEXT:     %[[C2:.+]] = arith.constant 2.000000e+00 : f64
+// CHECK-NEXT:     %[[C3:.+]] = arith.constant 4.000000e+00 : f64
+// CHECK-NEXT:     %{{.+}} = math.acos %[[C0]] : f32
+// CHECK-NEXT:     %{{.+}} = math.acos %[[C1]] : f80
+// CHECK-NEXT:     %{{.+}} = math.acos %[[C2]] : f64
+// CHECK-NEXT:     %{{.+}} = math.acos %[[C3]] : f64
+// CHECK-NEXT:     return
+// CHECK-NEXT:   }
+// CHECK-NEXT: }