diff --git a/Userland/Libraries/LibC/malloc.cpp b/Userland/Libraries/LibC/malloc.cpp
index 8819f020db..e4268fb76c 100644
--- a/Userland/Libraries/LibC/malloc.cpp
+++ b/Userland/Libraries/LibC/malloc.cpp
@@ -425,6 +425,37 @@ void* malloc(size_t size)
     return ptr;
 }
 
+// This is a Microsoft extension, and is not found on other Unix-like systems.
+// FIXME: Implement aligned_alloc() instead
+//
+// This is used in libc++ to implement C++17 aligned new/delete.
+//
+// Both Unix-y alternatives to _aligned_malloc(), the C11 aligned_alloc() and
+// posix_memalign() say that the resulting pointer can be deallocated with
+// regular free(), which means that the allocator has to keep track of the
+// requested alignments. By contrast, _aligned_malloc() is paired with
+// _aligned_free(), so it can be easily implemented on top of malloc().
+void* _aligned_malloc(size_t size, size_t alignment)
+{
+    if (__builtin_popcount(alignment) != 1) {
+        errno = EINVAL;
+        return nullptr;
+    }
+    alignment = max(alignment, sizeof(void*));
+    if (Checked<size_t>::addition_would_overflow(size, alignment)) {
+        errno = ENOMEM;
+        return nullptr;
+    }
+    void* ptr = malloc(size + alignment);
+    if (!ptr) {
+        errno = ENOMEM;
+        return nullptr;
+    }
+    auto aligned_ptr = (void*)(((FlatPtr)ptr + alignment) & ~(alignment - 1));
+    ((void**)aligned_ptr)[-1] = ptr;
+    return aligned_ptr;
+}
+
 void free(void* ptr)
 {
     MemoryAuditingSuppressor suppressor;
@@ -434,6 +465,12 @@ void free(void* ptr)
     free_impl(ptr);
 }
 
+void _aligned_free(void* ptr)
+{
+    if (ptr)
+        free(((void**)ptr)[-1]);
+}
+
 void* calloc(size_t count, size_t size)
 {
     MemoryAuditingSuppressor suppressor;
diff --git a/Userland/Libraries/LibC/stdlib.h b/Userland/Libraries/LibC/stdlib.h
index 8d624a6aa8..56f067d8c1 100644
--- a/Userland/Libraries/LibC/stdlib.h
+++ b/Userland/Libraries/LibC/stdlib.h
@@ -25,6 +25,8 @@ size_t malloc_good_size(size_t);
 void serenity_dump_malloc_stats(void);
 void free(void*);
 __attribute__((alloc_size(2))) void* realloc(void* ptr, size_t);
+__attribute__((malloc, alloc_size(1), alloc_align(2))) void* _aligned_malloc(size_t size, size_t alignment);
+void _aligned_free(void* memblock);
 char* getenv(const char* name);
 char* secure_getenv(const char* name);
 int putenv(char*);