SN 1961i was a supernova that was discovered in June 1961 in the Messier 61 (NGC 4303) galaxy, by Milton L. Humason at the Palomar Observatory,[1] the brightest of 16 supernovae found at Palomar that year.[2] Although it was originally considered by Fritz Zwicky to be the prototype of a type III supernova, subsequent researchers have classified it as a type II supernova.[3] [4]