diff --git a/NEWS b/NEWS
index d4ada857fa..717ae69b65 100644
--- a/NEWS
+++ b/NEWS
@@ -109,6 +109,11 @@ with all sufficient information, see the ChangeLog file or Redmine
 
   * Description set by Thread#name= is now visible on Windows 10.
 
+* KeyError
+
+  * KeyError#receiver [Feature #12063]
+  * KeyError#key      [Feature #12063]
+
 === Stdlib updates (outstanding ones only)
 
 * Bundler
diff --git a/error.c b/error.c
index a12c5d206d..ffdd1a4ef1 100644
--- a/error.c
+++ b/error.c
@@ -815,7 +815,7 @@ VALUE rb_mErrno;
 static VALUE rb_eNOERROR;
 
 static ID id_new, id_cause, id_message, id_backtrace;
-static ID id_name, id_args, id_Errno, id_errno, id_i_path;
+static ID id_name, id_key, id_args, id_Errno, id_errno, id_i_path;
 static ID id_receiver, id_iseq, id_local_variables;
 static ID id_private_call_p;
 extern ID ruby_static_id_status;
@@ -1547,6 +1547,37 @@ rb_invalid_str(const char *str, const char *type)
     rb_raise(rb_eArgError, "invalid value for %s: %+"PRIsVALUE, type, s);
 }
 
+static VALUE
+key_err_receiver(VALUE self)
+{
+    VALUE recv;
+
+    recv = rb_ivar_lookup(self, id_receiver, Qundef);
+    if (recv != Qundef) return recv;
+    rb_raise(rb_eArgError, "no receiver is available");
+}
+
+static VALUE
+key_err_key(VALUE self)
+{
+    VALUE key;
+
+    key = rb_ivar_lookup(self, id_key, Qundef);
+    if (key != Qundef) return key;
+    rb_raise(rb_eArgError, "no key is available");
+}
+
+VALUE
+rb_key_err_new(VALUE mesg, VALUE recv, VALUE key)
+{
+    VALUE exc = rb_obj_alloc(rb_eKeyError);
+    rb_ivar_set(exc, id_mesg, mesg);
+    rb_ivar_set(exc, id_bt, Qnil);
+    rb_ivar_set(exc, id_key, key);
+    rb_ivar_set(exc, id_receiver, recv);
+    return exc;
+}
+
 /*
  * call-seq:
  *   SyntaxError.new([msg])  -> syntax_error
@@ -2161,6 +2192,8 @@ Init_Exception(void)
     rb_eArgError      = rb_define_class("ArgumentError", rb_eStandardError);
     rb_eIndexError    = rb_define_class("IndexError", rb_eStandardError);
     rb_eKeyError      = rb_define_class("KeyError", rb_eIndexError);
+    rb_define_method(rb_eKeyError, "receiver", key_err_receiver, 0);
+    rb_define_method(rb_eKeyError, "key", key_err_key, 0);
     rb_eRangeError    = rb_define_class("RangeError", rb_eStandardError);
 
     rb_eScriptError = rb_define_class("ScriptError", rb_eException);
@@ -2216,6 +2249,7 @@ Init_Exception(void)
     id_message = rb_intern_const("message");
     id_backtrace = rb_intern_const("backtrace");
     id_name = rb_intern_const("name");
+    id_key = rb_intern_const("key");
     id_args = rb_intern_const("args");
     id_receiver = rb_intern_const("receiver");
     id_private_call_p = rb_intern_const("private_call?");
diff --git a/hash.c b/hash.c
index bc02696b30..7198e8a9d8 100644
--- a/hash.c
+++ b/hash.c
@@ -912,7 +912,7 @@ rb_hash_fetch_m(int argc, VALUE *argv, VALUE hash)
 		desc = rb_any_to_s(key);
 	    }
 	    desc = rb_str_ellipsize(desc, 65);
-	    rb_raise(rb_eKeyError, "key not found: %"PRIsVALUE, desc);
+	    rb_key_err_raise(rb_sprintf("key not found: %"PRIsVALUE, desc), hash, key);
 	}
 	return argv[1];
     }
@@ -3375,7 +3375,7 @@ env_fetch(int argc, VALUE *argv)
     if (!env) {
 	if (block_given) return rb_yield(key);
 	if (argc == 1) {
-	    rb_raise(rb_eKeyError, "key not found: \"%"PRIsVALUE"\"", key);
+	    rb_key_err_raise(rb_sprintf("key not found: \"%"PRIsVALUE"\"", key), envtbl, key);
 	}
 	return argv[1];
     }
diff --git a/internal.h b/internal.h
index 3e6b30a235..3ff731c2de 100644
--- a/internal.h
+++ b/internal.h
@@ -1156,6 +1156,9 @@ VALUE rb_name_err_new(VALUE mesg, VALUE recv, VALUE method);
     rb_exc_raise(rb_name_err_new(mesg, recv, name))
 #define rb_name_err_raise(mesg, recv, name) \
     rb_name_err_raise_str(rb_fstring_cstr(mesg), (recv), (name))
+VALUE rb_key_err_new(VALUE mesg, VALUE recv, VALUE name);
+#define rb_key_err_raise(mesg, recv, name) \
+    rb_exc_raise(rb_key_err_new(mesg, recv, name))
 NORETURN(void ruby_deprecated_internal_feature(const char *));
 #define DEPRECATED_INTERNAL_FEATURE(func) \
     (ruby_deprecated_internal_feature(func), UNREACHABLE)
diff --git a/sprintf.c b/sprintf.c
index 2bd4966a1b..a956381cd4 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -633,7 +633,7 @@ rb_str_format(int argc, const VALUE *argv, VALUE fmt)
 		    }
 		    nextvalue = rb_hash_default_value(hash, sym);
 		    if (NIL_P(nextvalue)) {
-			rb_enc_raise(enc, rb_eKeyError, "key%.*s not found", len, start);
+			rb_key_err_raise(rb_enc_sprintf(enc, "key%.*s not found", len, start), hash, sym);
 		    }
 		}
 		if (term == '}') goto format_s;
diff --git a/test/ruby/test_env.rb b/test/ruby/test_env.rb
index 29c058339f..d136ba75fa 100644
--- a/test/ruby/test_env.rb
+++ b/test/ruby/test_env.rb
@@ -122,9 +122,11 @@ class TestEnv < Test::Unit::TestCase
     assert_equal("foo", ENV.fetch("test"))
     ENV.delete("test")
     feature8649 = '[ruby-core:56062] [Feature #8649]'
-    assert_raise_with_message(KeyError, 'key not found: "test"', feature8649) do
+    e = assert_raise_with_message(KeyError, 'key not found: "test"', feature8649) do
       ENV.fetch("test")
     end
+    assert_same(ENV, e.receiver)
+    assert_equal("test", e.key)
     assert_equal("foo", ENV.fetch("test", "foo"))
     assert_equal("bar", ENV.fetch("test") { "bar" })
     assert_equal("bar", ENV.fetch("test", "foo") { "bar" })
diff --git a/test/ruby/test_hash.rb b/test/ruby/test_hash.rb
index 8fb1c17003..ebc622a827 100644
--- a/test/ruby/test_hash.rb
+++ b/test/ruby/test_hash.rb
@@ -531,6 +531,8 @@ class TestHash < Test::Unit::TestCase
     e = assert_raise(KeyError) { @h.fetch('gumby'*20) }
     assert_match(/key not found: "gumbygumby/, e.message)
     assert_match(/\.\.\.\z/, e.message)
+    assert_same(@h, e.receiver)
+    assert_equal('gumby'*20, e.key)
   end
 
   def test_key2?
@@ -591,9 +593,11 @@ class TestHash < Test::Unit::TestCase
     assert_equal(4, res.length)
     assert_equal %w( three two one nil ), res
 
-    assert_raise KeyError do
+    e = assert_raise KeyError do
       @h.fetch_values(3, 'invalid')
     end
+    assert_same(@h, e.receiver)
+    assert_equal('invalid', e.key)
 
     res = @h.fetch_values(3, 'invalid') { |k| k.upcase }
     assert_equal %w( three INVALID ), res
diff --git a/test/ruby/test_sprintf.rb b/test/ruby/test_sprintf.rb
index b46f5189e2..a07ac7908b 100644
--- a/test/ruby/test_sprintf.rb
+++ b/test/ruby/test_sprintf.rb
@@ -452,7 +452,10 @@ class TestSprintf < Test::Unit::TestCase
     assert_raise_with_message(ArgumentError, "named<key2> after numbered") {sprintf("%1$<key2>s", :key => "value")}
     assert_raise_with_message(ArgumentError, "named<key2> after unnumbered(2)") {sprintf("%s%s%<key2>s", "foo", "bar", :key => "value")}
     assert_raise_with_message(ArgumentError, "named<key2> after <key>") {sprintf("%<key><key2>s", :key => "value")}
-    assert_raise_with_message(KeyError, "key<key> not found") {sprintf("%<key>s", {})}
+    h = {}
+    e = assert_raise_with_message(KeyError, "key<key> not found") {sprintf("%<key>s", h)}
+    assert_same(h, e.receiver)
+    assert_equal(:key, e.key)
   end
 
   def test_named_untyped_enc