Augustus (plural Augusti; aw-GUST-əs, Classical Latin: [au̯ˈɡʊstʊs]; "majestic", "great" or "venerable") was an ancient Roman title given as both name and title to Gaius Julius Caesar Octavianus (often referred to simply as Augustus), Rome's first Emperor. On his death, it became an official title of his successor, and was so used by Roman emperors thereafter. The feminine form Augusta was used for Roman empresses and other female members of the Imperial family. The masculine and feminine forms originated in the time of the Roman Republic, in connection with things considered divine or sacred in traditional Roman religion. Their use as titles for major and minor Roman deities of the Empire associated the Imperial system and Imperial family with traditional Roman virtues and the divine will, and may be considered a feature of the Roman Imperial cult.

In Rome's Greek-speaking provinces, "Augustus" was translated as Sebastos (Σεβαστός, "venerable"), or Hellenised as Augoustos (Αὔγουστος); these titles continued to be used in the Byzantine Empire until the Fall of Constantinople in 1453, although they gradually lost their imperial exclusivity.

After the fall of the western Roman Empire, the title "Augustus" would later be incorporated into the style of the Holy Roman Emperor, a precedent set by Charlemagne who used the title serenissimus Augustus. As such, Augustus was sometimes also used as a name for men of aristocratic birth, especially in the lands of the Holy Roman Empire. It remains a given name for males.