diff --git a/doc/string/eql_p.rdoc b/doc/string/eql_p.rdoc
new file mode 100644
index 0000000000..85409c5ed6
--- /dev/null
+++ b/doc/string/eql_p.rdoc
@@ -0,0 +1,18 @@
+Returns whether +self+ and +object+ have the same length and content:
+
+  s = 'foo'
+  s.eql?('foo')  # => true
+  s.eql?('food') # => false
+  s.eql?('FOO')  # => false
+
+Returns +false+ if the two strings' encodings are not compatible:
+
+  s0 = "äöü"                           # => "äöü"
+  s1 = s0.encode(Encoding::ISO_8859_1) # => "\xE4\xF6\xFC"
+  s0.encoding                          # => #<Encoding:UTF-8>
+  s1.encoding                          # => #<Encoding:ISO-8859-1>
+  s0.eql?(s1)                          # => false
+
+See {Encodings}[rdoc-ref:encodings.rdoc].
+
+Related: see {Querying}[rdoc-ref:String@Querying].
diff --git a/string.c b/string.c
index 58fe632463..235ead3fa0 100644
--- a/string.c
+++ b/string.c
@@ -4243,17 +4243,7 @@ rb_str_equal(VALUE str1, VALUE str2)
  * call-seq:
  *   eql?(object) -> true or false
  *
- *  Returns +true+ if +object+ has the same length and content;
- *  as +self+; +false+ otherwise:
- *
- *    s = 'foo'
- *    s.eql?('foo') # => true
- *    s.eql?('food') # => false
- *    s.eql?('FOO') # => false
- *
- *  Returns +false+ if the two strings' encodings are not compatible:
- *
- *    "\u{e4 f6 fc}".encode(Encoding::ISO_8859_1).eql?("\u{c4 d6 dc}") # => false
+ * :include: doc/string/eql_p.rdoc
  *
  */