Supernova 1604, also known as Kepler's Supernova or Kepler's Star, was a supernova which occurred in the Milky Way, in the constellation Ophiuchus. As of 2007, it is the last supernova to have been unquestionably observed in our own galaxy, occurring no farther than 6 kiloparsecs or about 20,000 light-years from Earth. Visible to the naked eye, it was brighter at its peak than any other star in the night sky, and all the planets (other than Venus), with apparent magnitude −2.5.
The supernova was first observed on October 9, 1604. The German astronomer Johannes Kepler first saw it on October 17, subsequently named after himself. His book on the subject was entitled De Stella nova in pede Serpentarii (On the new star in Ophiuchus's foot).
It was the second supernova to be observed in a generation (after SN 1572 seen by Tycho Brahe in Cassiopeia). No further supernovae have since been observed with certainty in the Milky Way, though many others outside our galaxy have been seen.
The supernova remnant resulting from this supernova is considered to be one of the "prototypical" objects of its kind, and is still an object of much study in astronomy.