diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 631779a17a165..dd559df08cce6 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -519,10 +519,11 @@ impl String {
     /// between the two. Not all byte slices are valid strings, however: strings
     /// are required to be valid UTF-8. During this conversion,
     /// `from_utf8_lossy()` will replace any invalid UTF-8 sequences with
-    /// `U+FFFD REPLACEMENT CHARACTER`, which looks like this: �
+    /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], which looks like this: �
     ///
     /// [`u8`]: ../../std/primitive.u8.html
     /// [byteslice]: ../../std/primitive.slice.html
+    /// [U+FFFD]: ../char/constant.REPLACEMENT_CHARACTER.html
     ///
     /// If you are sure that the byte slice is valid UTF-8, and you don't want
     /// to incur the overhead of the conversion, there is an unsafe version
@@ -621,7 +622,7 @@ impl String {
     }
 
     /// Decode a UTF-16 encoded slice `v` into a `String`, replacing
-    /// invalid data with the replacement character (U+FFFD).
+    /// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
     ///
     /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
     /// `from_utf16_lossy` returns a `String` since the UTF-16 to UTF-8
@@ -629,6 +630,7 @@ impl String {
     ///
     /// [`from_utf8_lossy`]: #method.from_utf8_lossy
     /// [`Cow<'a, str>`]: ../borrow/enum.Cow.html
+    /// [U+FFFD]: ../char/constant.REPLACEMENT_CHARACTER.html
     ///
     /// # Examples
     ///
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 356534a91879c..54b17b0fbb320 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -244,7 +244,10 @@ impl Utf8Error {
     ///   The length provided is that of the invalid byte sequence
     ///   that starts at the index given by `valid_up_to()`.
     ///   Decoding should resume after that sequence
-    ///   (after inserting a U+FFFD REPLACEMENT CHARACTER) in case of lossy decoding.
+    ///   (after inserting a [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD]) in case of
+    ///   lossy decoding.
+    ///
+    /// [U+FFFD]: ../../std/char/constant.REPLACEMENT_CHARACTER.html
     #[stable(feature = "utf8_error_error_len", since = "1.20.0")]
     pub fn error_len(&self) -> Option<usize> {
         self.error_len.map(|len| len as usize)
diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index b2777f5c48541..2b87094926cf5 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -1175,9 +1175,9 @@ impl CStr {
     /// If the contents of the `CStr` are valid UTF-8 data, this
     /// function will return a [`Cow`]`::`[`Borrowed`]`(`[`&str`]`)`
     /// with the the corresponding [`&str`] slice. Otherwise, it will
-    /// replace any invalid UTF-8 sequences with `U+FFFD REPLACEMENT
-    /// CHARACTER` and return a [`Cow`]`::`[`Owned`]`(`[`String`]`)`
-    /// with the result.
+    /// replace any invalid UTF-8 sequences with
+    /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD] and return a
+    /// [`Cow`]`::`[`Owned`]`(`[`String`]`)` with the result.
     ///
     /// > **Note**: This method is currently implemented to check for validity
     /// > after a constant-time cast, but it is planned to alter its definition
@@ -1189,6 +1189,7 @@ impl CStr {
     /// [`Owned`]: ../borrow/enum.Cow.html#variant.Owned
     /// [`str`]: ../primitive.str.html
     /// [`String`]: ../string/struct.String.html
+    /// [U+FFFD]: ../char/constant.REPLACEMENT_CHARACTER.html
     ///
     /// # Examples
     ///
diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index 9e501a84e05ec..6bcd62dbd59c2 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -520,10 +520,12 @@ impl OsStr {
 
     /// Converts an `OsStr` to a [`Cow`]`<`[`str`]`>`.
     ///
-    /// Any non-Unicode sequences are replaced with U+FFFD REPLACEMENT CHARACTER.
+    /// Any non-Unicode sequences are replaced with
+    /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD].
     ///
     /// [`Cow`]: ../../std/borrow/enum.Cow.html
     /// [`str`]: ../../std/primitive.str.html
+    /// [U+FFFD]: ../../std/char/constant.REPLACEMENT_CHARACTER.html
     ///
     /// # Examples
     ///
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 688a7e99f10ed..ca8be75fab5be 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -1737,9 +1737,11 @@ impl Path {
 
     /// Converts a `Path` to a [`Cow<str>`].
     ///
-    /// Any non-Unicode sequences are replaced with U+FFFD REPLACEMENT CHARACTER.
+    /// Any non-Unicode sequences are replaced with
+    /// [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD].
     ///
     /// [`Cow<str>`]: ../borrow/enum.Cow.html
+    /// [U+FFFD]: ../char/constant.REPLACEMENT_CHARACTER.html
     ///
     /// # Examples
     ///
diff --git a/src/libstd/sys/windows/ext/ffi.rs b/src/libstd/sys/windows/ext/ffi.rs
index 98d4355248990..bae0d02786a09 100644
--- a/src/libstd/sys/windows/ext/ffi.rs
+++ b/src/libstd/sys/windows/ext/ffi.rs
@@ -31,7 +31,7 @@
 //!
 //! If Rust code *does* need to look into those strings, it can
 //! convert them to valid UTF-8, possibly lossily, by substituting
-//! invalid sequences with U+FFFD REPLACEMENT CHARACTER, as is
+//! invalid sequences with [`U+FFFD REPLACEMENT CHARACTER`][U+FFFD], as is
 //! conventionally done in other Rust APIs that deal with string
 //! encodings.
 //!
@@ -65,6 +65,7 @@
 //! [`from_wide`]: trait.OsStringExt.html#tymethod.from_wide
 //! [`encode_wide`]: trait.OsStrExt.html#tymethod.encode_wide
 //! [`collect`]: ../../../iter/trait.Iterator.html#method.collect
+//! [U+FFFD]: ../../../char/constant.REPLACEMENT_CHARACTER.html
 
 #![stable(feature = "rust1", since = "1.0.0")]