M99 was discovered on March 15, 1781 by Messier's colleague and friend, Pierre Méchain, together with the nearby situated M98 and M100. Charles Messier measured its position and included it in his catalog on April 13, 1781, immediately before finishing the third, final published edition.

M99, although situated in constellation Coma Berenices, is one of the bright spiral members of the Virgo Cluster of galaxies. It is of type Sc, rotates clockwise (unlike the nearby spiral M100), and is unusually asymmetric.

Three supernovae have been recorded in M99: the type II supernova 1967H, mag 14, in June 1967. type II supernova 1972Q, mag 15.6, on Dec 16, 1972, and 1986I of type I, mag 14, on May 17, 1986.

M99 was the second nebula, or galaxy, to be recognized as a spiral, by Lord Rosse in spring 1846, about one year after his first discovery of a spiral, M51, in spring 1845.

Visually, it looks like elliptical nebula with brighter core. It is quite faint in 8" telescope.