C89 may refer to:
Science and technology C89 (C version) or ANSI C, a C programming-language revision NGC 6087 (Caldwell catalogue: C89), an open cluster in the constellation Norma
Other uses Ruy Lopez (ECO code: C60–C99), a chess opening Night Work (Women) Convention (Revised), 1948, an ILO convention Sylvania Airport (FAA LID), Wisconsin, US
See also HMNZS Royalist (C89), a 1942 New Zealand Royal navy cruiser KNHC, a radio station in Seattle, Washington known as C89.5