Caesar ( Latin: [ˈkae̯.sar] English pl. Caesars; Latin pl. Caesares; in Greek: Καῖσᾰρ Kaîsar) is a title of imperial character. It derives from the cognomen of Julius Caesar, the Roman dictator. The change from being a familial name to a title adopted by the Roman Emperors can be dated to about 68/69 AD, the so-called " Year of the Four Emperors ".

Caesar is considered by many historians to be one of the greatest military commanders in history. His cognomen was subsequently adopted as a synonym for " Emperor "; the title " Caesar " was used throughout the Roman Empire, giving rise to modern cognates such as Kaiser and Tsar.