Messier 61 (also known as M61 or NGC 4303) is an intermediate barred spiral galaxy in the Virgo Cluster of galaxies. It was discovered by Barnaba Oriani on May 5, 1779. This was six days before Charles Messier observed the same galaxy, but had mistaken it as a comet.

M61 is one of the largest members of Virgo Cluster, and is designated to belong to a smaller section of the galaxy cluster known as the S Cloud. It has an active galactic nucleus and is classified as a starburst galaxy containing a massive nuclear star cluster with an estimated mass of 10⁵ solar massesand an age of 4 million years, as well as a central candidate supermassive black hole weighing around 5×10⁶ M_☉ solar masses. cohabiting with an older massive star cluster as well as a likely older starburst. Evidence of significant star formation and active bright nebulae appears across M61’s disk. Unlike most late-type spiral galaxies within the Virgo Cluster, M61 shows an unusual abundance of neutral hydrogen (H I)