diff --git a/libc/test/src/math/atanf_test.cpp b/libc/test/src/math/atanf_test.cpp
@@ -0,0 +1,65 @@
+//===-- Unittests for atanf -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/math/atanf.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+#include "utils/UnitTest/FPMatcher.h"
+#include "utils/UnitTest/Test.h"
+#include <math.h>
+
+#include <errno.h>
+#include <stdint.h>
+
+#include <initializer_list>
+
+using FPBits = __llvm_libc::fputil::FPBits<float>;
+
+namespace mpfr = __llvm_libc::testing::mpfr;
+
+DECLARE_SPECIAL_CONSTANTS(float)
+
+TEST(LlvmLibcAtanfTest, SpecialNumbers) {
+  errno = 0;
+  __llvm_libc::fputil::clear_except(FE_ALL_EXCEPT);
+  EXPECT_FP_EQ(aNaN, __llvm_libc::atanf(aNaN));
+  EXPECT_FP_EXCEPTION(FE_INVALID);
+  EXPECT_MATH_ERRNO(0);
+
+  __llvm_libc::fputil::clear_except(FE_ALL_EXCEPT);
+  EXPECT_FP_EQ(0.0f, __llvm_libc::atanf(0.0f));
+  EXPECT_FP_EXCEPTION(0);
+  EXPECT_MATH_ERRNO(0);
+
+  __llvm_libc::fputil::clear_except(FE_ALL_EXCEPT);
+  EXPECT_FP_EQ(-0.0f, __llvm_libc::atanf(-0.0f));
+  EXPECT_FP_EXCEPTION(0);
+  EXPECT_MATH_ERRNO(0);
+}
+
+TEST(LlvmLibcAtanfTest, InFloatRange) {
+  constexpr uint32_t COUNT = 1000000;
+  const uint32_t STEP = FPBits(inf).uintval() / COUNT;
+  for (uint32_t i = 0, v = 0; i <= COUNT; ++i, v += STEP) {
+    float x = float(FPBits(v));
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan, x,
+                                   __llvm_libc::atanf(x), 0.5);
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan, -x,
+                                   __llvm_libc::atanf(-x), 0.5);
+  }
+}
+
+// For small values, tanh(x) is x.
+TEST(LlvmLibcAtanfTest, SpecialValues) {
+  for (uint32_t v : {0x3d8d6b23U, 0x3feefcfbU, 0xbd8d6b23U, 0xbfeefcfbU,
+                     0x7F800000U, 0xFF800000U}) {
+    float x = float(FPBits(v));
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan, x,
+                                   __llvm_libc::atanf(x), 0.5);
+  }
+}
diff --git a/libc/test/src/math/exhaustive/CMakeLists.txt b/libc/test/src/math/exhaustive/CMakeLists.txt
@@ -307,3 +307,21 @@ add_fp_unittest(
   LINK_LIBRARIES
     -lpthread
 )
+
+add_fp_unittest(
+  atanf_test
+  NO_RUN_POSTBUILD
+  NEED_MPFR
+  SUITE
+    libc_math_exhaustive_tests
+  SRCS
+    atanf_test.cpp
+  DEPENDS
+    .exhaustive_test
+    libc.include.math
+    libc.src.math.atanf
+    libc.src.__support.FPUtil.fputil
+  LINK_LIBRARIES
+    -lpthread
+)
+
diff --git a/libc/test/src/math/exhaustive/atanf_test.cpp b/libc/test/src/math/exhaustive/atanf_test.cpp
@@ -0,0 +1,76 @@
+//===-- Exhaustive test for atanf -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "exhaustive_test.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/math/atanf.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+#include <thread>
+
+using FPBits = __llvm_libc::fputil::FPBits<float>;
+
+namespace mpfr = __llvm_libc::testing::mpfr;
+
+struct LlvmLibcAtanfExhaustiveTest : public LlvmLibcExhaustiveTest<uint32_t> {
+  bool check(uint32_t start, uint32_t stop,
+             mpfr::RoundingMode rounding) override {
+    mpfr::ForceRoundingMode r(rounding);
+    uint32_t bits = start;
+    bool result = true;
+    do {
+      FPBits xbits(bits);
+      float x = float(xbits);
+      result &= EXPECT_MPFR_MATCH(mpfr::Operation::Atan, x,
+                                  __llvm_libc::atanf(x), 0.5, rounding);
+    } while (bits++ < stop);
+    return result;
+  }
+};
+
+static const int NUM_THREADS = std::thread::hardware_concurrency();
+
+// Range: [0, 1.0];
+static const uint32_t POS_START = 0x0000'0000U;
+static const uint32_t POS_STOP = FPBits::inf().uintval();
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, PostiveRangeRoundNearestTieToEven) {
+  test_full_range(POS_START, POS_STOP, mpfr::RoundingMode::Nearest);
+}
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, PostiveRangeRoundUp) {
+  test_full_range(POS_START, POS_STOP, mpfr::RoundingMode::Upward);
+}
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, PostiveRangeRoundDown) {
+  test_full_range(POS_START, POS_STOP, mpfr::RoundingMode::Downward);
+}
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, PostiveRangeRoundTowardZero) {
+  test_full_range(POS_START, POS_STOP, mpfr::RoundingMode::TowardZero);
+}
+
+// Range: [-1.0, 0];
+static const uint32_t NEG_START = 0x8000'0000U;
+static const uint32_t NEG_STOP = FPBits::neg_inf().uintval();
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, NegativeRangeRoundNearestTieToEven) {
+  test_full_range(NEG_START, NEG_STOP, mpfr::RoundingMode::Nearest);
+}
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, NegativeRangeRoundUp) {
+  test_full_range(NEG_START, NEG_STOP, mpfr::RoundingMode::Upward);
+}
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, NegativeRangeRoundDown) {
+  test_full_range(NEG_START, NEG_STOP, mpfr::RoundingMode::Downward);
+}
+
+TEST_F(LlvmLibcAtanfExhaustiveTest, NegativeRangeRoundTowardZero) {
+  test_full_range(NEG_START, NEG_STOP, mpfr::RoundingMode::TowardZero);
+}
diff --git a/libc/test/src/math/explogxf_test.cpp b/libc/test/src/math/explogxf_test.cpp
@@ -1,4 +1,4 @@
-//===-- Unittests for explogxf --------------------------------------------===//
+//===-- Unittests for supfuncf --------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.

diff --git a/libc/test/src/math/inv_trigf_utils_test.cpp b/libc/test/src/math/inv_trigf_utils_test.cpp
@@ -0,0 +1,32 @@
+//===-- Unittests for supfuncf --------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "in_float_range_test_helper.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/math/generic/inv_trigf_utils.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+#include "utils/UnitTest/FPMatcher.h"
+#include "utils/UnitTest/Test.h"
+#include <math.h>
+
+namespace mpfr = __llvm_libc::testing::mpfr;
+
+DECLARE_SPECIAL_CONSTANTS(float)
+
+constexpr int def_count = 100003;
+constexpr float def_prec = 0.500001f;
+
+TEST(LlvmLibcAtanfPosTest, InFloatRange) {
+  CHECK_DATA(0.0f, inf, mpfr::Operation::Atan, __llvm_libc::atan_eval, isfinite,
+             def_count, def_prec);
+}
+
+TEST(LlvmLibcAtanfNegTest, InFloatRange) {
+  CHECK_DATA(-0.0f, neg_inf, mpfr::Operation::Atan, __llvm_libc::atan_eval,
+             isfinite, def_count, def_prec);
+}
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -182,6 +182,12 @@ class MPFRNumber {
     return result;
   }
 
+  MPFRNumber atan() const {
+    MPFRNumber result(*this);
+    mpfr_atan(result.value, value, mpfr_rounding);
+    return result;
+  }
+
   MPFRNumber atanh() const {
     MPFRNumber result(*this);
     mpfr_atanh(result.value, value, mpfr_rounding);
@@ -506,6 +512,8 @@ unary_operation(Operation op, InputType input, unsigned int precision,
   switch (op) {
   case Operation::Abs:
     return mpfrInput.abs();
+  case Operation::Atan:
+    return mpfrInput.atan();
   case Operation::Atanh:
     return mpfrInput.atanh();
   case Operation::Ceil:

diff --git a/libc/utils/MPFRWrapper/MPFRUtils.h b/libc/utils/MPFRWrapper/MPFRUtils.h
@@ -25,6 +25,7 @@ enum class Operation : int {
   // and output floating point numbers are of the same kind.
   BeginUnaryOperationsSingleOutput,
   Abs,
+  Atan,
   Atanh,
   Ceil,
   Cos,
-Original file line number
+Diff line change
@@ Expand Up / @@ -25,6 +25,7 @@ enum class Operation : int { @@
       // and output floating point numbers are of the same kind.
       BeginUnaryOperationsSingleOutput,
       Abs,
+      Atan,
       Atanh,
       Ceil,
       Cos,
@@ Expand Down @@