diff --git a/libc/src/__support/CPP/ArrayRef.h b/libc/src/__support/CPP/ArrayRef.h
--- a/libc/src/__support/CPP/ArrayRef.h
+++ b/libc/src/__support/CPP/ArrayRef.h
@@ -58,7 +58,7 @@
 
   bool empty() const { return size() == 0; }
 
-  auto operator[](size_t Index) const { return data()[Index]; }
+  auto &operator[](size_t Index) const { return data()[Index]; }
 
   // slice(n, m) - Chop off the first N elements of the array, and keep M
   // elements in the array.
@@ -115,6 +115,11 @@
   using Impl::Impl;
 
 public:
+  // Construct an ArrayRef from void * pointer.
+  // |Length| is the byte length of the array pointed to by |Data|.
+  ArrayRef(const void *Data, size_t Length)
+      : Impl(reinterpret_cast<const T *>(Data), Length / sizeof(T)) {}
+
   // From Array.
   template <size_t N> ArrayRef(const Array<T, N> &Arr) : Impl(Arr.Data, N) {}
 };
@@ -129,6 +134,11 @@
   using Impl::Impl;
 
 public:
+  // Construct an ArrayRef from void * pointer.
+  // |Length| is the byte length of the array pointed to by |Data|.
+  MutableArrayRef(void *Data, size_t Length)
+      : Impl(reinterpret_cast<T *>(Data), Length / sizeof(T)) {}
+
   // From Array.
   template <size_t N> MutableArrayRef(Array<T, N> &Arr) : Impl(Arr.Data, N) {}
 
diff --git a/libc/test/src/__support/CPP/arrayref_test.cpp b/libc/test/src/__support/CPP/arrayref_test.cpp
--- a/libc/test/src/__support/CPP/arrayref_test.cpp
+++ b/libc/test/src/__support/CPP/arrayref_test.cpp
@@ -218,5 +218,22 @@
   }
 }
 
+TEST(LlvmLibcArrayRefTest, ConstructFromVoidPtr) {
+  unsigned data[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  void *ptr = data;
+  const void *const_ptr = data;
+  ArrayRef<unsigned> ref(const_ptr, sizeof(data));
+  MutableArrayRef<unsigned> mutable_ref(ptr, sizeof(data));
+  ASSERT_EQ(ref.size(), sizeof(data) / sizeof(unsigned));
+  ASSERT_EQ(mutable_ref.size(), sizeof(data) / sizeof(unsigned));
+
+  unsigned val = 123;
+  for (size_t i = 0; i < sizeof(data) / sizeof(unsigned); ++i)
+    mutable_ref[i] = val;
+
+  for (size_t i = 0; i < sizeof(data) / sizeof(unsigned); ++i)
+    ASSERT_EQ(ref[i], val);
+}
+
 } // namespace cpp
 } // namespace __llvm_libc