diff --git a/Tests/LibC/CMakeLists.txt b/Tests/LibC/CMakeLists.txt
index 18b60fb65a..e73c846c83 100644
--- a/Tests/LibC/CMakeLists.txt
+++ b/Tests/LibC/CMakeLists.txt
@@ -3,6 +3,7 @@ set(TEST_SOURCES
     TestAssert.cpp
     TestCType.cpp
     TestEnvironment.cpp
+    TestFenv.cpp
     TestIo.cpp
     TestLibCExec.cpp
     TestLibCGrp.cpp
@@ -40,6 +41,8 @@ set(TEST_SOURCES
 
 set_source_files_properties(TestMath.cpp PROPERTIES COMPILE_FLAGS "-fno-builtin")
 set_source_files_properties(TestStrtodAccuracy.cpp PROPERTIES COMPILE_FLAGS "-fno-builtin-strtod")
+# Don't assume default rounding behavior is used for testing rounding behavior modifications.
+set_source_files_properties(TestFenv.cpp PROPERTIES COMPILE_FLAGS "-frounding-math")
 
 foreach(source IN LISTS TEST_SOURCES)
     serenity_test("${source}" LibC)
diff --git a/Tests/LibC/TestFenv.cpp b/Tests/LibC/TestFenv.cpp
new file mode 100644
index 0000000000..91f9d50dca
--- /dev/null
+++ b/Tests/LibC/TestFenv.cpp
@@ -0,0 +1,121 @@
+/*
+ * Copyright (c) 2023, kleines Filmröllchen <filmroellchen@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+#include <fenv.h>
+
+// TODO: Add tests for floating-point exception management.
+
+static constexpr auto reset_rounding_mode = [] { fesetround(FE_TONEAREST); };
+
+#if !ARCH(RISCV64)
+#    define TOMAXMAGNITUDE_DECAYS_TO_TONEAREST
+#endif
+
+TEST_CASE(float_round_up)
+{
+    // Non-default rounding mode should not escape files with -frounding-math.
+    ScopeGuard rounding_mode_guard = reset_rounding_mode;
+
+    fesetround(FE_UPWARD);
+    EXPECT_EQ(0.1f + 0.2f, 0.3f);
+    EXPECT_EQ(0.1f + 0.3f, 0.40000004f);
+    EXPECT_EQ(0.1f + 0.4f, 0.50000006f);
+    EXPECT_EQ(-1.f + -0.1f, -1.0999999f);
+    EXPECT_EQ(1.f + 0.1f, 1.1f);
+}
+
+TEST_CASE(float_round_down)
+{
+    ScopeGuard rounding_mode_guard = reset_rounding_mode;
+
+    fesetround(FE_DOWNWARD);
+    EXPECT_EQ(0.1f + 0.2f, 0.29999998f);
+    EXPECT_EQ(0.1f + 0.3f, 0.4f);
+    EXPECT_EQ(0.1f + 0.4f, 0.5f);
+    EXPECT_EQ(-1.f + -0.1f, -1.1f);
+    EXPECT_EQ(1.f + 0.1f, 1.0999999f);
+}
+
+TEST_CASE(float_round_to_zero)
+{
+    ScopeGuard rounding_mode_guard = reset_rounding_mode;
+
+    fesetround(FE_TOWARDZERO);
+    EXPECT_EQ(0.1f + 0.2f, 0.29999998f);
+    EXPECT_EQ(0.1f + 0.3f, 0.4f);
+    EXPECT_EQ(0.1f + 0.4f, 0.5f);
+    EXPECT_EQ(-1.f + -0.1f, -1.0999999f);
+    EXPECT_EQ(1.f + 0.1f, 1.0999999f);
+}
+
+TEST_CASE(float_round_to_nearest)
+{
+    ScopeGuard rounding_mode_guard = reset_rounding_mode;
+
+    fesetround(FE_TONEAREST);
+    EXPECT_EQ(0.1f + 0.2f, 0.3f);
+    EXPECT_EQ(0.1f + 0.3f, 0.4f);
+    EXPECT_EQ(0.1f + 0.4f, 0.5f);
+    EXPECT_EQ(-1.f + -0.1f, -1.1f);
+    EXPECT_EQ(1.f + 0.1f, 1.1f);
+    EXPECT_EQ(1.f + 5.9604645e-08f, 1.f);
+}
+
+TEST_CASE(float_round_to_max_magnitude)
+{
+    ScopeGuard rounding_mode_guard = reset_rounding_mode;
+
+    fesetround(FE_TOMAXMAGNITUDE);
+    EXPECT_EQ(0.1f + 0.2f, 0.3f);
+    EXPECT_EQ(0.1f + 0.3f, 0.4f);
+    EXPECT_EQ(0.1f + 0.4f, 0.5f);
+    EXPECT_EQ(-1.f + -0.1f, -1.1f);
+    EXPECT_EQ(1.f + 0.1f, 1.1f);
+#ifdef TOMAXMAGNITUDE_DECAYS_TO_TONEAREST
+    EXPECT_EQ(1.f + 5.9604645e-08f, 1.f);
+#else
+    EXPECT_EQ(1.f + 5.9604645e-08f, 1.0000001f);
+#endif
+}
+
+TEST_CASE(store_round_in_env)
+{
+    ScopeGuard rounding_mode_guard = reset_rounding_mode;
+
+    fesetround(FE_DOWNWARD);
+    fenv_t env;
+    fegetenv(&env);
+    fesetround(FE_UPWARD);
+    // This result only happens under upward rounding.
+    EXPECT_EQ(-1.f + -0.1f, -1.0999999f);
+    fesetenv(&env);
+    // ... and this only under downward rounding.
+    EXPECT_EQ(-1.f + -0.1f, -1.1f);
+}
+
+TEST_CASE(save_restore_round)
+{
+    ScopeGuard rounding_mode_guard = reset_rounding_mode;
+
+    fesetround(FE_DOWNWARD);
+    auto rounding_mode = fegetround();
+    EXPECT_EQ(rounding_mode, FE_DOWNWARD);
+
+    fesetround(FE_UPWARD);
+    EXPECT_EQ(fegetround(), FE_UPWARD);
+    EXPECT_EQ(-1.f + -0.1f, -1.0999999f);
+    fesetround(rounding_mode);
+    EXPECT_EQ(-1.f + -0.1f, -1.1f);
+
+    fesetround(FE_TOMAXMAGNITUDE);
+#ifdef TOMAXMAGNITUDE_DECAYS_TO_TONEAREST
+    // Max-magnitude rounding is not supported by x86, so we expect fesetround to decay it to some other rounding mode.
+    EXPECT_EQ(fegetround(), FE_TONEAREST);
+#else
+    EXPECT_EQ(fegetround(), FE_TOMAXMAGNITUDE);
+#endif
+}