Otto is a masculine German given name and a surname. It originates as an Old High German short form (variants Audo, Odo, Udo) of Germanic names beginning in aud-, an element meaning "wealth, prosperity".

The name is recorded from the 7th century (Odo, son of Uro, courtier of Sigebert III). It was the name of three 10th-century German kings, the first of whom was Otto I the Great, the first Holy Roman Emperor, founder of the Ottonian dynasty.

The Gothic form of the prefix was auda- (as in e.g. Audaþius), the Anglo-Saxon form was ead- (as in e.g. Eadmund), and the Old Norse form was auð-.

Due to Otto von Bismarck, the given name Otto was strongly associated with the German Empire in the later 19th century. It was comparatively frequently given in the United States (presumably in German American families) during the 1880s to 1890s, remaining in the top 100 most popular masculine given names in the US throughout 1880–1898, but its popularity decreased significantly after 1900 with increasing anti-German sentiment leading up to World War I; it fell below rank 200 in 1919, below rank 500 in 1947, and below rank 1000 in 1975. It re-entered the top-1000 most popular given names in the US in the 2010s, ranking 696th as of 2013.

The given name Otis arose from an English surname, which was in turn derived from Ode, a variant form of Odo, Otto.