diff --git a/tests/std/include/new_counter.hpp b/tests/std/include/new_counter.hpp
index 2954dfd7d9a..2bcd0429041 100644
--- a/tests/std/include/new_counter.hpp
+++ b/tests/std/include/new_counter.hpp
@@ -33,9 +33,11 @@ void* operator new(size_t size) {
     return p;
 }
 
+#ifdef __cpp_aligned_new
 void* operator new(size_t, std::align_val_t) {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 void* operator new(size_t size, const std::nothrow_t&) noexcept {
     if (std_testing::g_total_news == std_testing::g_maximum_news) {
@@ -50,9 +52,11 @@ void* operator new(size_t size, const std::nothrow_t&) noexcept {
     return malloc(size);
 }
 
+#ifdef __cpp_aligned_new
 void* operator new(size_t, std::align_val_t, const std::nothrow_t&) noexcept {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 void operator delete(void* ptr) noexcept {
     ::operator delete(ptr, std::nothrow);
@@ -62,9 +66,11 @@ void operator delete(void* ptr, size_t) noexcept {
     ::operator delete(ptr, std::nothrow);
 }
 
+#ifdef __cpp_aligned_new
 void operator delete(void*, std::align_val_t) noexcept {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 void operator delete(void* ptr, const std::nothrow_t&) noexcept {
     if (ptr) {
@@ -74,25 +80,31 @@ void operator delete(void* ptr, const std::nothrow_t&) noexcept {
     }
 }
 
+#ifdef __cpp_aligned_new
 void operator delete(void*, std::align_val_t, const std::nothrow_t&) noexcept {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 void* operator new[](size_t size) {
     return ::operator new(size);
 }
 
+#ifdef __cpp_aligned_new
 void* operator new[](size_t, std::align_val_t) {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 void* operator new[](size_t size, const std::nothrow_t&) noexcept {
     return ::operator new(size, std::nothrow);
 }
 
+#ifdef __cpp_aligned_new
 void* operator new[](size_t, std::align_val_t, const std::nothrow_t&) noexcept {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 void operator delete[](void* ptr) noexcept {
     ::operator delete(ptr);
@@ -102,6 +114,7 @@ void operator delete[](void* ptr, size_t size) noexcept {
     ::operator delete(ptr, size);
 }
 
+#ifdef __cpp_aligned_new
 void operator delete[](void*, std::align_val_t) noexcept {
     abort();
 }
@@ -109,13 +122,16 @@ void operator delete[](void*, std::align_val_t) noexcept {
 void operator delete[](void*, size_t, std::align_val_t) noexcept {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 void operator delete[](void* ptr, const std::nothrow_t&) noexcept {
     ::operator delete(ptr, std::nothrow);
 }
 
+#ifdef __cpp_aligned_new
 void operator delete[](void*, std::align_val_t, const std::nothrow_t&) noexcept {
     abort();
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 #pragma warning(pop)
diff --git a/tests/std/include/test_header_units_and_modules.hpp b/tests/std/include/test_header_units_and_modules.hpp
index 71aaf6a6632..8115b163da2 100644
--- a/tests/std/include/test_header_units_and_modules.hpp
+++ b/tests/std/include/test_header_units_and_modules.hpp
@@ -542,7 +542,9 @@ void test_new() {
 
     static_assert(is_class_v<bad_alloc>);
     static_assert(is_class_v<bad_array_new_length>);
+#ifdef __cpp_aligned_new
     static_assert(is_same_v<underlying_type_t<align_val_t>, size_t>);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     static_assert(is_class_v<nothrow_t>);
 
     bool caught_bad_alloc = false;
diff --git a/tests/std/tests/GH_005504_avoid_function_call_wrapping/test.cpp b/tests/std/tests/GH_005504_avoid_function_call_wrapping/test.cpp
index bd3df479759..1d8c12648b4 100644
--- a/tests/std/tests/GH_005504_avoid_function_call_wrapping/test.cpp
+++ b/tests/std/tests/GH_005504_avoid_function_call_wrapping/test.cpp
@@ -38,6 +38,7 @@ void operator delete(void* const mem) noexcept {
     free(mem);
 }
 
+#ifdef __cpp_aligned_new
 void* operator new(const size_t size, const align_val_t al) {
     ++alloc_count;
     return check_alloc(_aligned_malloc(adjust_alloc_size(size), static_cast<size_t>(al)));
@@ -47,6 +48,7 @@ void operator delete(void* const mem, align_val_t) noexcept {
     ++dealloc_count;
     _aligned_free(mem);
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 struct alloc_checker {
     explicit alloc_checker(const int expected_delta_) : expected_delta(expected_delta_) {}
@@ -90,7 +92,9 @@ struct alignas(128) large_callable {
     const int context = 1729;
 
     int operator()(const copy_counter& counter) const noexcept {
+#ifdef __cpp_aligned_new
         assert((reinterpret_cast<uintptr_t>(this) & 0x7f) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
         assert(context == 1729);
         return counter.count;
     }
diff --git a/tests/std/tests/P0035R4_over_aligned_allocation/test.cpp b/tests/std/tests/P0035R4_over_aligned_allocation/test.cpp
index ac66ca4024a..78e26b528bd 100644
--- a/tests/std/tests/P0035R4_over_aligned_allocation/test.cpp
+++ b/tests/std/tests/P0035R4_over_aligned_allocation/test.cpp
@@ -1,6 +1,10 @@
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+#if !defined(__cpp_aligned_new)
+#error overaligned allocation does not work with /Zc:alignedNew-
+#endif
+
 #define _ENABLE_EXTENDED_ALIGNED_STORAGE
 #define _HAS_DEPRECATED_TEMPORARY_BUFFER 1
 #define _SILENCE_CXX17_TEMPORARY_BUFFER_DEPRECATION_WARNING
diff --git a/tests/std/tests/P0220R1_any/test.cpp b/tests/std/tests/P0220R1_any/test.cpp
index 391bb7b0ed1..6ce91a8f653 100644
--- a/tests/std/tests/P0220R1_any/test.cpp
+++ b/tests/std/tests/P0220R1_any/test.cpp
@@ -26,6 +26,10 @@
 // Yes, this is an awkward hand process; notably the required headers can change without notice. We should investigate
 // running the libc++ tests directly in all of our configurations so we needn't replicate this subset of files.
 
+#if !defined(__cpp_aligned_new)
+#error This test relies on libc++ machinery which assumes overaligned allocation support since C++17
+#endif
+
 #define _LIBCXX_IN_DEVCRT
 #include <msvc_stdlib_force_include.h> // Must precede any other libc++ headers
 #include <stdlib.h>
diff --git a/tests/std/tests/P0220R1_polymorphic_memory_resources/test.cpp b/tests/std/tests/P0220R1_polymorphic_memory_resources/test.cpp
index 12dd09f6891..31d32431edf 100644
--- a/tests/std/tests/P0220R1_polymorphic_memory_resources/test.cpp
+++ b/tests/std/tests/P0220R1_polymorphic_memory_resources/test.cpp
@@ -1,6 +1,10 @@
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+#if !defined(__cpp_aligned_new)
+#error pmr does not completely work with /Zc:alignedNew-
+#endif
+
 #define _SILENCE_CXX23_ALIGNED_UNION_DEPRECATION_WARNING
 
 #include <algorithm>
diff --git a/tests/std/tests/P0674R1_make_shared_for_arrays/test.cpp b/tests/std/tests/P0674R1_make_shared_for_arrays/test.cpp
index ae408c850b8..274f4db81f7 100644
--- a/tests/std/tests/P0674R1_make_shared_for_arrays/test.cpp
+++ b/tests/std/tests/P0674R1_make_shared_for_arrays/test.cpp
@@ -156,7 +156,9 @@ void test_make_shared_not_array() {
 
     shared_ptr<HighlyAligned> p5 = make_shared<HighlyAligned>();
     assert_shared_use_get(p5);
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p5.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     assert(p5->a == 0 && p5->b == 0 && p5->c == 0 && p5->d == 0);
 }
 
@@ -209,7 +211,9 @@ void test_make_shared_array_known_bounds() {
 
     shared_ptr<HighlyAligned[6]> p6 = make_shared<HighlyAligned[6]>();
     assert_shared_use_get(p6);
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p6.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     for (int i = 0; i < 6; ++i) {
         assert(p6[i].a == 0 && p6[i].b == 0 && p6[i].c == 0 && p6[i].d == 0);
     }
@@ -279,7 +283,9 @@ void test_make_shared_array_unknown_bounds() {
 
     shared_ptr<HighlyAligned[]> p7 = make_shared<HighlyAligned[]>(7u);
     assert_shared_use_get(p7);
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p7.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     for (int i = 0; i < 7; ++i) {
         assert(p7[i].a == 0 && p7[i].b == 0 && p7[i].c == 0 && p7[i].d == 0);
     }
@@ -422,7 +428,9 @@ void test_allocate_shared_not_array() {
     {
         shared_ptr<HighlyAligned> p5 = allocate_shared<HighlyAligned>(a5);
         assert_shared_use_get(p5);
+#ifdef __cpp_aligned_new
         assert(reinterpret_cast<uintptr_t>(p5.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
         assert(p5->a == 0 && p5->b == 0 && p5->c == 0 && p5->d == 0);
     }
     assert_construct_destruct_equal();
@@ -502,7 +510,9 @@ void test_allocate_shared_array_known_bounds() {
     {
         shared_ptr<HighlyAligned[6]> p6 = allocate_shared<HighlyAligned[6]>(a6);
         assert_shared_use_get(p6);
+#ifdef __cpp_aligned_new
         assert(reinterpret_cast<uintptr_t>(p6.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
         for (int i = 0; i < 6; ++i) {
             assert(p6[i].a == 0 && p6[i].b == 0 && p6[i].c == 0 && p6[i].d == 0);
         }
@@ -603,7 +613,9 @@ void test_allocate_shared_array_unknown_bounds() {
     {
         shared_ptr<HighlyAligned[]> p7 = allocate_shared<HighlyAligned[]>(a7, 7u);
         assert_shared_use_get(p7);
+#ifdef __cpp_aligned_new
         assert(reinterpret_cast<uintptr_t>(p7.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
         for (int i = 0; i < 7; ++i) {
             assert(p7[i].a == 0 && p7[i].b == 0 && p7[i].c == 0 && p7[i].d == 0);
         }
diff --git a/tests/std/tests/P1020R1_smart_pointer_for_overwrite/test.cpp b/tests/std/tests/P1020R1_smart_pointer_for_overwrite/test.cpp
index 39371d080e4..a4bec125c76 100644
--- a/tests/std/tests/P1020R1_smart_pointer_for_overwrite/test.cpp
+++ b/tests/std/tests/P1020R1_smart_pointer_for_overwrite/test.cpp
@@ -47,6 +47,7 @@ void* operator new(size_t size, const nothrow_t&) noexcept {
     return result;
 }
 
+#ifdef __cpp_aligned_new
 void* operator new(size_t size, align_val_t align) {
     void* const p = ::operator new(size, align, nothrow);
 
@@ -66,6 +67,7 @@ void* operator new(size_t size, align_val_t align, const nothrow_t&) noexcept {
 
     return result;
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 template <typename T, typename = void>
 struct unique_is_for_overwritable : false_type {};
@@ -188,7 +190,9 @@ void test_make_shared_for_overwrite() {
     assert(p1->value == initializedValue);
 
     auto p2 = make_shared_for_overwrite_assert<HighlyAligned>();
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p2.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     assert_uninitialized(addressof(*p2), sizeof(HighlyAligned));
 
     auto p3 = make_shared_for_overwrite_assert<int[100]>();
@@ -202,7 +206,9 @@ void test_make_shared_for_overwrite() {
     }
 
     auto p5 = make_shared_for_overwrite_assert<HighlyAligned[10]>();
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p5.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     assert_uninitialized(addressof(p5[0]), sizeof(HighlyAligned) * 10u);
 
     auto p6 = make_shared_for_overwrite_assert<DefaultInitializableInt[]>(100u);
@@ -225,7 +231,9 @@ void test_make_shared_for_overwrite() {
     auto p9 = make_shared_for_overwrite_assert<int[]>(0u); // p9 cannot be dereferenced
 
     auto p10 = make_shared_for_overwrite_assert<HighlyAligned[]>(10u);
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p10.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     assert_uninitialized(addressof(p10[0]), sizeof(HighlyAligned) * 10u);
 
     test_make_shared_init_destruct_order<ReportAddress[5]>(); // success one dimensional
@@ -280,7 +288,9 @@ void test_allocate_shared_for_overwrite() {
 
     allocator<HighlyAligned> a2{};
     auto p2 = allocate_shared_for_overwrite_assert<HighlyAligned>(a2);
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p2.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     assert_uninitialized(addressof(*p2), sizeof(HighlyAligned));
 
     auto p3 = allocate_shared_for_overwrite_assert<int[100]>(a0);
@@ -294,7 +304,9 @@ void test_allocate_shared_for_overwrite() {
     }
 
     auto p5 = allocate_shared_for_overwrite_assert<HighlyAligned[10]>(a2);
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p5.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     assert_uninitialized(addressof(p5[0]), sizeof(HighlyAligned) * 10u);
 
     auto p6 = allocate_shared_for_overwrite_assert<DefaultInitializableInt[]>(a1, 100u);
@@ -317,7 +329,9 @@ void test_allocate_shared_for_overwrite() {
     auto p9 = allocate_shared_for_overwrite_assert<int[]>(a0, 0u); // p9 cannot be dereferenced
 
     auto p10 = allocate_shared_for_overwrite_assert<HighlyAligned[]>(a2, 10u);
+#ifdef __cpp_aligned_new
     assert(reinterpret_cast<uintptr_t>(p10.get()) % alignof(HighlyAligned) == 0);
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
     assert_uninitialized(addressof(p10[0]), sizeof(HighlyAligned) * 10u);
 
     test_allocate_shared_init_destruct_order<ReportAddress[5]>(); // success one dimensional
diff --git a/tests/std/tests/P2502R2_generator/test.cpp b/tests/std/tests/P2502R2_generator/test.cpp
index a95255cb4e6..0d525a80493 100644
--- a/tests/std/tests/P2502R2_generator/test.cpp
+++ b/tests/std/tests/P2502R2_generator/test.cpp
@@ -306,9 +306,11 @@ void dynamic_allocator_test() {
     test_one<gen_traits<int>, int, int&&, int&&>(
         g(allocator_arg, StatefulAlloc<float>{1729}, 1024), views::iota(0, 1024));
 #endif // ^^^ no workaround ^^^
+#ifdef __cpp_aligned_new
     pmr::synchronized_pool_resource pool;
     test_one<gen_traits<int>, int, int&&, int&&>(
         g(allocator_arg, pmr::polymorphic_allocator<>{&pool}, 1024), views::iota(0, 1024));
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 }
 
 static atomic<bool> allow_allocation{true};
@@ -330,6 +332,7 @@ void operator delete(void* const p, size_t) noexcept {
     free(p);
 }
 
+#ifdef __cpp_aligned_new
 void* operator new(const size_t n, const align_val_t al) {
     if (allow_allocation) {
         if (void* const result = ::_aligned_malloc(n, static_cast<size_t>(al))) {
@@ -346,6 +349,7 @@ void operator delete(void* const p, align_val_t) noexcept {
 void operator delete(void* const p, size_t, align_val_t) noexcept {
     ::_aligned_free(p);
 }
+#endif // ^^^ defined(__cpp_aligned_new) ^^^
 
 class malloc_resource final : public pmr::memory_resource {
 private: