(101869) 1999 MM is an unnamed, eccentric asteroid of the Apollo group, classified as a near-Earth object and potentially hazardous asteroid, approximately half a kilometer in diameter. It was discovered on 20 June 1999, by the Lowell Observatory Near-Earth-Object Search (LONEOS) at its U.S. Anderson Mesa Station in Flagstaff, Arizona. The first observation was made by Catalina Sky Survey just 8 days before its discovery. Based on its absolute magnitude of 19.3, its diameter is between 350 and 900 meters, assuming an albedo in the range of 0.05 to 0.25.