diff --git a/doc/string/bytesplice.rdoc b/doc/string/bytesplice.rdoc
new file mode 100644
index 0000000000..5689ef4a2b
--- /dev/null
+++ b/doc/string/bytesplice.rdoc
@@ -0,0 +1,66 @@
+Replaces <i>target bytes</i> in +self+ with <i>source bytes</i> from the given string +str+;
+returns +self+.
+
+In the first form, arguments +offset+ and +length+ determine the target bytes,
+and the source bytes are all of the given +str+:
+
+  '0123456789'.bytesplice(0, 3, 'abc')  # => "abc3456789"
+  '0123456789'.bytesplice(3, 3, 'abc')  # => "012abc6789"
+  '0123456789'.bytesplice(0, 50, 'abc') # => "abc"
+  '0123456789'.bytesplice(50, 3, 'abc') # Raises IndexError.
+
+The counts of the target bytes and source source bytes may be different:
+
+  '0123456789'.bytesplice(0, 6, 'abc') # => "abc6789"      # Shorter source.
+  '0123456789'.bytesplice(0, 1, 'abc') # => "abc123456789" # Shorter target.
+
+And either count may be zero (i.e., specifying an empty string):
+
+  '0123456789'.bytesplice(0, 3, '')    # => "3456789"       # Empty source.
+  '0123456789'.bytesplice(0, 0, 'abc') # => "abc0123456789" # Empty target.
+
+In the second form, just as in the first,
+arugments +offset+ and +length+ determine the target bytes;
+argument +str+ _contains_ the source bytes,
+and the additional arguments +str_offset+ and +str_length+
+determine the actual source bytes:
+
+  '0123456789'.bytesplice(0, 3, 'abc', 0, 3) # => "abc3456789"
+  '0123456789'.bytesplice(0, 3, 'abc', 1, 1) # => "b3456789"      # Shorter source.
+  '0123456789'.bytesplice(0, 1, 'abc', 0, 3) # => "abc123456789"  # Shorter target.
+  '0123456789'.bytesplice(0, 3, 'abc', 1, 0) # => "3456789"       # Empty source.
+  '0123456789'.bytesplice(0, 0, 'abc', 0, 3) # => "abc0123456789" # Empty target.
+
+In the third form, argument +range+ determines the target bytes
+and the source bytes are all of the given +str+:
+
+  '0123456789'.bytesplice(0..2, 'abc')  # => "abc3456789"
+  '0123456789'.bytesplice(3..5, 'abc')  # => "012abc6789"
+  '0123456789'.bytesplice(0..5, 'abc')  # => "abc6789"       # Shorter source.
+  '0123456789'.bytesplice(0..0, 'abc')  # => "abc123456789"  # Shorter target.
+  '0123456789'.bytesplice(0..2, '')     # => "3456789"       # Empty source.
+  '0123456789'.bytesplice(0...0, 'abc') # => "abc0123456789" # Empty target.
+
+In the fourth form, just as in the third,
+arugment +range+ determines the target bytes;
+argument +str+ _contains_ the source bytes,
+and the additional argument +str_range+
+determines the actual source bytes:
+
+  '0123456789'.bytesplice(0..2, 'abc', 0..2)  # => "abc3456789"
+  '0123456789'.bytesplice(3..5, 'abc', 0..2)  # => "012abc6789"
+  '0123456789'.bytesplice(0..2, 'abc', 0..1)  # => "ab3456789"     # Shorter source.
+  '0123456789'.bytesplice(0..1, 'abc', 0..2)  # => "abc23456789"   # Shorter target.
+  '0123456789'.bytesplice(0..2, 'abc', 0...0) # => "3456789"       # Empty source.
+  '0123456789'.bytesplice(0...0, 'abc', 0..2) # => "abc0123456789" # Empty target.
+
+In any of the forms, the beginnings and endings of both source and target
+must be on character boundaries.
+
+In these examples, +self+ has five 3-byte characters,
+and so has character boundaries at offsets 0, 3, 6, 9, 12, and 15.
+
+  'こんにちは'.bytesplice(0, 3, 'abc') # => "abcんにちは"
+  'こんにちは'.bytesplice(1, 3, 'abc') # Raises IndexError.
+  'こんにちは'.bytesplice(0, 2, 'abc') # Raises IndexError.
+
diff --git a/string.c b/string.c
index 183d1336d7..6069a8751b 100644
--- a/string.c
+++ b/string.c
@@ -6913,23 +6913,12 @@ str_check_beg_len(VALUE str, long *beg, long *len)
 
 /*
  *  call-seq:
- *    bytesplice(index, length, str) -> string
- *    bytesplice(index, length, str, str_index, str_length) -> string
- *    bytesplice(range, str) -> string
- *    bytesplice(range, str, str_range) -> string
+ *    bytesplice(offset, length, str) -> self
+ *    bytesplice(offset, length, str, str_offset, str_length) -> self
+ *    bytesplice(range, str) -> self
+ *    bytesplice(range, str, str_range) -> self
  *
- *  Replaces some or all of the content of +self+ with +str+, and returns +self+.
- *  The portion of the string affected is determined using
- *  the same criteria as String#byteslice, except that +length+ cannot be omitted.
- *  If the replacement string is not the same length as the text it is replacing,
- *  the string will be adjusted accordingly.
- *
- *  If +str_index+ and +str_length+, or +str_range+ are given, the content of +self+ is replaced by str.byteslice(str_index, str_length) or str.byteslice(str_range); however the substring of +str+ is not allocated as a new string.
- *
- *  The form that take an Integer will raise an IndexError if the value is out
- *  of range; the Range form will raise a RangeError.
- *  If the beginning or ending offset does not land on character (codepoint)
- *  boundary, an IndexError will be raised.
+ *  :include: doc/string/bytesplice.rdoc
  */
 
 static VALUE
diff --git a/string.rb b/string.rb
index a5ff79a62c..a14c81ba2d 100644
--- a/string.rb
+++ b/string.rb
@@ -391,6 +391,7 @@
 #
 # _Substitution_
 #
+# - #bytesplice: Replaces bytes of +self+ with bytes from a given string; returns +self+.
 # - #sub!: Replaces the first substring that matches a given pattern with a given replacement string;
 #   returns +self+ if any changes, +nil+ otherwise.
 # - #gsub!: Replaces each substring that matches a given pattern with a given replacement string;