Nova Cygni 1975 (V1500 Cygni) was one of the most dramatic fast novae on record. It was discovered on 29 August 1975, soared to magnitude 2.0 the next day (altering the familiar outline of the Northern Cross in Cygnus), then dimmed by 3 magnitudes over the next three days and a total of 7 magnitudes in 45 days. It was the fastest, largest amplitude, and second most intrinsically bright nova of the twentieth century (only Nova Puppis 1942 was brighter).

Data collected since the outburst indicate that V1500 Cyg (Nova Cygni's variable star name) is an AM Herculis star in which the white dwarf primary has such a powerful magnetic field that it inhibits the formation of an accretion disk and almost synchronizes the rotational period with the orbital period. V1500 Cyg is the 13th confirmed AM Her-type system and has the second longest orbital period (about 3.3 hours).