diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md
--- a/flang/docs/Extensions.md
+++ b/flang/docs/Extensions.md
@@ -289,6 +289,8 @@
   fixed form source by a '0' in column 6, can contain spaces
   between the letters of the word INCLUDE, and can have a
   numeric character literal kind prefix on the file name.
+* Intrinsic procedures TAND and ATAND. Constant folding is currently
+  not supported for these procedures but this is planned.
 
 ### Extensions supported when enabled by options
 
diff --git a/flang/include/flang/Optimizer/Builder/IntrinsicCall.h b/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
--- a/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
+++ b/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
@@ -316,6 +316,7 @@
                                     llvm::ArrayRef<fir::ExtendedValue>);
   fir::ExtendedValue genSum(mlir::Type, llvm::ArrayRef<fir::ExtendedValue>);
   void genSystemClock(llvm::ArrayRef<fir::ExtendedValue>);
+  mlir::Value genTand(mlir::Type, llvm::ArrayRef<mlir::Value>);
   mlir::Value genTrailz(mlir::Type, llvm::ArrayRef<mlir::Value>);
   fir::ExtendedValue genTransfer(mlir::Type,
                                  llvm::ArrayRef<fir::ExtendedValue>);
diff --git a/flang/lib/Optimizer/Builder/IntrinsicCall.cpp b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
--- a/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
+++ b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
@@ -511,6 +511,7 @@
      &I::genSystemClock,
      {{{"count", asAddr}, {"count_rate", asAddr}, {"count_max", asAddr}}},
      /*isElemental=*/false},
+    {"tand", &I::genTand},
     {"trailz", &I::genTrailz},
     {"transfer",
      &I::genTransfer,
@@ -4997,6 +4998,21 @@
       .getResults()[0];
 }
 
+// TAND
+mlir::Value IntrinsicLibrary::genTand(mlir::Type resultType,
+                                      llvm::ArrayRef<mlir::Value> args) {
+  assert(args.size() == 1);
+  mlir::MLIRContext *context = builder.getContext();
+  mlir::FunctionType ftype =
+      mlir::FunctionType::get(context, {resultType}, {args[0].getType()});
+  llvm::APFloat pi = llvm::APFloat(llvm::numbers::pi);
+  mlir::Value dfactor = builder.createRealConstant(
+      loc, mlir::FloatType::getF64(context), pi / llvm::APFloat(180.0));
+  mlir::Value factor = builder.createConvert(loc, args[0].getType(), dfactor);
+  mlir::Value arg = builder.create<mlir::arith::MulFOp>(loc, args[0], factor);
+  return getRuntimeCallGenerator("tan", ftype)(builder, loc, {arg});
+}
+
 // TRAILZ
 mlir::Value IntrinsicLibrary::genTrailz(mlir::Type resultType,
                                         llvm::ArrayRef<mlir::Value> args) {
diff --git a/flang/test/Lower/Intrinsics/tand.f90 b/flang/test/Lower/Intrinsics/tand.f90
new file mode 100644
--- /dev/null
+++ b/flang/test/Lower/Intrinsics/tand.f90
@@ -0,0 +1,26 @@
+! RUN: bbc -emit-fir %s -o - | FileCheck %s --check-prefixes="CHECK,CHECK-FAST"
+! RUN: bbc --math-runtime=precise -emit-fir %s -o - | FileCheck %s --check-prefixes="CHECK,CHECK-PRECISE"
+! RUN: %flang_fc1 -emit-fir %s -o - | FileCheck %s --check-prefixes="CHECK,CHECK-FAST"
+
+function test_real4(x)
+  real :: x, test_real4
+  test_real4 = tand(x)
+end function
+
+! CHECK-LABEL: @_QPtest_real4
+! CHECK: %[[dfactor:.*]] = arith.constant 0.017453292519943295 : f64
+! CHECK: %[[factor:.*]] = fir.convert %[[dfactor]] : (f64) -> f32
+! CHECK: %[[arg:.*]] = arith.mulf %{{[A-Za-z0-9._]+}}, %[[factor]] fastmath<contract> : f32
+! CHECK-PRECISE: %{{.*}} = fir.call @tanf(%[[arg]]) fastmath<contract> : (f32) -> f32
+! CHECK-FAST: %{{.*}} = math.tan %[[arg]] fastmath<contract> : f32
+
+function test_real8(x)
+  real(8) :: x, test_real8
+  test_real8 = tand(x)
+end function
+
+! CHECK-LABEL: @_QPtest_real8
+! CHECK: %[[factor:.*]] = arith.constant 0.017453292519943295 : f64
+! CHECK: %[[arg:.*]] = arith.mulf %{{[A-Za-z0-9._]+}}, %[[factor]] fastmath<contract> : f64
+! CHECK-PRECISE: %{{.*}} = fir.call @tan(%[[arg]]) fastmath<contract> : (f64) -> f64
+! CHECK-FAST: %{{.*}} = math.tan %[[arg]] fastmath<contract> : f64