Caesar's Comet was a seven-day cometary outburst seen in July 44 BC. It was interpreted by Romans as a sign of the deification of recently assassinated dictator, Julius Caesar. It was perhaps the most famous comet of antiquity.

A great comet is a comet that becomes exceptionally bright. There is no official definition; often the term is attached to comets such as Halley's Comet, which during certain appearances are bright enough to be noticed by casual observers who are not looking for them, and become well known outside the astronomical community. Great comets appear at irregular, unpredictable intervals, on average about once per decade. Although comets are officially named after their discoverers, great comets are sometimes also referred to by the year in which they appeared great, using the formulation "The Great Comet of ...", followed by the year.