O23

O23 or O-23 may refer to:
 * HNLMS O 23, a submarine of the Royal Netherlands Navy
 * Osim International, a Singaporean company
 * Oxygen-23, an isotope of oxygen
 * Ranchaero Airport, in Butte County, California, United States; assigned FAA LID O23 until 2009
 * Thomas-Morse O-23, an observation aircraft of the United States Army Air Corps