(219774) 2001 YY145, provisional designation 2001 YY145 is a stony background asteroid and exceptionally slow rotator from the central region of the asteroid belt, approximately 1.5 kilometers (0.9 miles) in diameter. It was discovered on 18 December 2001, by astronomers with the Lowell Observatory Near-Earth-Object Search at Anderson Mesa Station near Flagstaff, Arizona, in the United States. The assumed S-type asteroid is likely elongated and has a rarely seen rotation period of 1007 hours, making it the 13th slowest rotator.