diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index f98dbf8a0bd..b29a86d58ed 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -4,7 +4,7 @@ use crate::traits;
 use crate::ty::adjustment::CoerceUnsizedInfo;
 use crate::ty::{self, Ty};
 use std::intrinsics::transmute_unchecked;
-use std::mem::{size_of, MaybeUninit};
+use std::mem::MaybeUninit;
 
 #[derive(Copy, Clone)]
 pub struct Erased<T: Copy> {
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 875c24c28e4..f3a4803e0d4 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -257,8 +257,6 @@ use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
 use core::marker::{PhantomData, Unsize};
-#[cfg(not(no_global_oom_handling))]
-use core::mem::size_of_val;
 use core::mem::{self, align_of_val_raw, forget, ManuallyDrop};
 use core::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn, Receiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 7dcaa59dcd1..5a4f9df614e 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -18,8 +18,6 @@ use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
 use core::marker::{PhantomData, Unsize};
-#[cfg(not(no_global_oom_handling))]
-use core::mem::size_of_val;
 use core::mem::{self, align_of_val_raw};
 use core::ops::{CoerceUnsized, Deref, DerefPure, DispatchFromDyn, Receiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs
index 6cdc1e00f47..efa0fd7b56c 100644
--- a/library/core/src/cell.rs
+++ b/library/core/src/cell.rs
@@ -253,7 +253,7 @@
 use crate::cmp::Ordering;
 use crate::fmt::{self, Debug, Display};
 use crate::marker::{PhantomData, Unsize};
-use crate::mem::{self, size_of};
+use crate::mem;
 use crate::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn};
 use crate::ptr::{self, NonNull};
 
diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index 89e0b670995..28397fe4619 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -65,7 +65,6 @@
 
 use crate::marker::DiscriminantKind;
 use crate::marker::Tuple;
-use crate::mem::align_of;
 use crate::ptr;
 use crate::ub_checks;
 
diff --git a/library/core/src/prelude/common.rs b/library/core/src/prelude/common.rs
index afc6817aa1d..2a0331ef7b2 100644
--- a/library/core/src/prelude/common.rs
+++ b/library/core/src/prelude/common.rs
@@ -14,6 +14,9 @@ pub use crate::ops::{Drop, Fn, FnMut, FnOnce};
 #[stable(feature = "core_prelude", since = "1.4.0")]
 #[doc(no_inline)]
 pub use crate::mem::drop;
+#[stable(feature = "size_of_prelude", since = "CURRENT_RUSTC_VERSION")]
+#[doc(no_inline)]
+pub use crate::mem::{align_of, align_of_val, size_of, size_of_val};
 
 // Re-exported types and traits
 #[stable(feature = "core_prelude", since = "1.4.0")]
diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs
index 8e3447d0b1b..6661f6ee78b 100644
--- a/library/core/src/ptr/mod.rs
+++ b/library/core/src/ptr/mod.rs
@@ -415,7 +415,7 @@ use crate::intrinsics;
 use crate::marker::FnPtr;
 use crate::ub_checks;
 
-use crate::mem::{self, align_of, size_of, MaybeUninit};
+use crate::mem::{self, MaybeUninit};
 
 mod alignment;
 #[unstable(feature = "ptr_alignment_type", issue = "102070")]
diff --git a/library/core/src/slice/raw.rs b/library/core/src/slice/raw.rs
index 29a12f106c5..3f4305866e6 100644
--- a/library/core/src/slice/raw.rs
+++ b/library/core/src/slice/raw.rs
@@ -1,7 +1,6 @@
 //! Free functions to create `&[T]` and `&mut [T]`.
 
 use crate::array;
-use crate::mem::{align_of, size_of};
 use crate::ops::Range;
 use crate::ptr;
 use crate::ub_checks;
diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs
index 232ec589093..482bd19705c 100644
--- a/library/core/src/sync/atomic.rs
+++ b/library/core/src/sync/atomic.rs
@@ -1296,7 +1296,6 @@ impl<T> AtomicPtr<T> {
     #[cfg(target_has_atomic_equal_alignment = "ptr")]
     #[unstable(feature = "atomic_from_mut", issue = "76314")]
     pub fn from_mut(v: &mut *mut T) -> &mut Self {
-        use crate::mem::align_of;
         let [] = [(); align_of::<AtomicPtr<()>>() - align_of::<*mut ()>()];
         // SAFETY:
         //  - the mutable reference guarantees unique ownership.
@@ -2286,7 +2285,6 @@ macro_rules! atomic_int {
             #[$cfg_align]
             #[unstable(feature = "atomic_from_mut", issue = "76314")]
             pub fn from_mut(v: &mut $int_type) -> &mut Self {
-                use crate::mem::align_of;
                 let [] = [(); align_of::<Self>() - align_of::<$int_type>()];
                 // SAFETY:
                 //  - the mutable reference guarantees unique ownership.
@@ -2354,7 +2352,6 @@ macro_rules! atomic_int {
             #[$cfg_align]
             #[unstable(feature = "atomic_from_mut", issue = "76314")]
             pub fn from_mut_slice(v: &mut [$int_type]) -> &mut [Self] {
-                use crate::mem::align_of;
                 let [] = [(); align_of::<Self>() - align_of::<$int_type>()];
                 // SAFETY:
                 //  - the mutable reference guarantees unique ownership.
diff --git a/library/portable-simd/crates/core_simd/src/simd/ptr/const_ptr.rs b/library/portable-simd/crates/core_simd/src/simd/ptr/const_ptr.rs
index 0f1719206c9..cbffbc564cf 100644
--- a/library/portable-simd/crates/core_simd/src/simd/ptr/const_ptr.rs
+++ b/library/portable-simd/crates/core_simd/src/simd/ptr/const_ptr.rs
@@ -96,7 +96,7 @@ where
     fn cast<U>(self) -> Self::CastPtr<U> {
         // SimdElement currently requires zero-sized metadata, so this should never fail.
         // If this ever changes, `simd_cast_ptr` should produce a post-mono error.
-        use core::{mem::size_of, ptr::Pointee};
+        use core::ptr::Pointee;
         assert_eq!(size_of::<<T as Pointee>::Metadata>(), 0);
         assert_eq!(size_of::<<U as Pointee>::Metadata>(), 0);
 
diff --git a/library/portable-simd/crates/core_simd/src/simd/ptr/mut_ptr.rs b/library/portable-simd/crates/core_simd/src/simd/ptr/mut_ptr.rs
index 7ba996d149c..6bc6ca3ac42 100644
--- a/library/portable-simd/crates/core_simd/src/simd/ptr/mut_ptr.rs
+++ b/library/portable-simd/crates/core_simd/src/simd/ptr/mut_ptr.rs
@@ -93,7 +93,7 @@ where
     fn cast<U>(self) -> Self::CastPtr<U> {
         // SimdElement currently requires zero-sized metadata, so this should never fail.
         // If this ever changes, `simd_cast_ptr` should produce a post-mono error.
-        use core::{mem::size_of, ptr::Pointee};
+        use core::ptr::Pointee;
         assert_eq!(size_of::<<T as Pointee>::Metadata>(), 0);
         assert_eq!(size_of::<<U as Pointee>::Metadata>(), 0);
 
diff --git a/library/proc_macro/src/bridge/fxhash.rs b/library/proc_macro/src/bridge/fxhash.rs
index f9f74c63fc4..9fb79eabd05 100644
--- a/library/proc_macro/src/bridge/fxhash.rs
+++ b/library/proc_macro/src/bridge/fxhash.rs
@@ -7,7 +7,6 @@
 use std::collections::HashMap;
 use std::hash::BuildHasherDefault;
 use std::hash::Hasher;
-use std::mem::size_of;
 use std::ops::BitXor;
 
 /// Type alias for a hashmap using the `fx` hash algorithm.
diff --git a/library/std/src/io/error/repr_bitpacked.rs b/library/std/src/io/error/repr_bitpacked.rs
index 6f8d5e37775..c9d3934ad70 100644
--- a/library/std/src/io/error/repr_bitpacked.rs
+++ b/library/std/src/io/error/repr_bitpacked.rs
@@ -104,7 +104,6 @@
 
 use super::{Custom, ErrorData, ErrorKind, RawOsError, SimpleMessage};
 use core::marker::PhantomData;
-use core::mem::{align_of, size_of};
 use core::ptr::{self, NonNull};
 
 // The 2 least-significant bits are used as tag.
diff --git a/library/std/src/os/unix/net/ancillary.rs b/library/std/src/os/unix/net/ancillary.rs
index 0597fdcbd72..fe8e2be9372 100644
--- a/library/std/src/os/unix/net/ancillary.rs
+++ b/library/std/src/os/unix/net/ancillary.rs
@@ -3,7 +3,7 @@
 use super::{sockaddr_un, SocketAddr};
 use crate::io::{self, IoSlice, IoSliceMut};
 use crate::marker::PhantomData;
-use crate::mem::{size_of, zeroed};
+use crate::mem::zeroed;
 use crate::os::unix::io::RawFd;
 use crate::path::Path;
 use crate::ptr::{eq, read_unaligned};
diff --git a/library/std/src/prelude/common.rs b/library/std/src/prelude/common.rs
index 01936734d75..ceee3e33c3e 100644
--- a/library/std/src/prelude/common.rs
+++ b/library/std/src/prelude/common.rs
@@ -14,6 +14,9 @@ pub use crate::ops::{Drop, Fn, FnMut, FnOnce};
 #[stable(feature = "rust1", since = "1.0.0")]
 #[doc(no_inline)]
 pub use crate::mem::drop;
+#[stable(feature = "size_of_prelude", since = "CURRENT_RUSTC_VERSION")]
+#[doc(no_inline)]
+pub use crate::mem::{align_of, align_of_val, size_of, size_of_val};
 
 // Re-exported types and traits
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/std/src/prelude/mod.rs b/library/std/src/prelude/mod.rs
index 0bdbab716ad..2d4639342bf 100644
--- a/library/std/src/prelude/mod.rs
+++ b/library/std/src/prelude/mod.rs
@@ -36,6 +36,10 @@
 //!   operations for both destructors and overloading `()`.
 //! * <code>[std::mem]::[drop]</code>, a convenience function for explicitly
 //!   dropping a value.
+//! * <code>[std::mem]::{[size_of], [size_of_val]}</code>, to get the size of
+//!   a type or value.
+//! * <code>[std::mem]::{[align_of], [align_of_val]}</code>, to get the
+//!   alignment of a type or value.
 //! * <code>[std::boxed]::[Box]</code>, a way to allocate values on the heap.
 //! * <code>[std::borrow]::[ToOwned]</code>, the conversion trait that defines
 //!   [`to_owned`], the generic method for creating an owned type from a
diff --git a/tests/ui/resolve/filter-intrinsics.rs b/tests/ui/resolve/filter-intrinsics.rs
index c0956ef85af..8d6d22817dc 100644
--- a/tests/ui/resolve/filter-intrinsics.rs
+++ b/tests/ui/resolve/filter-intrinsics.rs
@@ -1,6 +1,6 @@
 fn main() {
-    // Should suggest only `std::mem::size_of`
-    let _ = size_of::<usize>();
+    // Should suggest only `std::mem::transmute`
+    let _ = transmute::<usize>();
     //~^ ERROR cannot find
 
     // Should suggest `std::intrinsics::fabsf64`,
diff --git a/tests/ui/resolve/filter-intrinsics.stderr b/tests/ui/resolve/filter-intrinsics.stderr
index cc1092dd0cf..9c9e92f6d4f 100644
--- a/tests/ui/resolve/filter-intrinsics.stderr
+++ b/tests/ui/resolve/filter-intrinsics.stderr
@@ -1,12 +1,12 @@
-error[E0425]: cannot find function `size_of` in this scope
+error[E0425]: cannot find function `transmute` in this scope
   --> $DIR/filter-intrinsics.rs:3:13
    |
-LL |     let _ = size_of::<usize>();
-   |             ^^^^^^^ not found in this scope
+LL |     let _ = transmute::<usize>();
+   |             ^^^^^^^^^ not found in this scope
    |
 help: consider importing this function
    |
-LL + use std::mem::size_of;
+LL + use std::mem::transmute;
    |
 
 error[E0425]: cannot find function `fabsf64` in this scope