Frederick III (1415-1493), also known as Frederick the Fat and Frederick the Peaceful, was the eldest son of the Inner Austrian duke Ernest the Iron, a member of the Habsburg dynasty. He became duke of Inner Austria in 1424 at the age of nine, but would not be awarded rule until 1435, with his younger brother Albert asserting his rights as co-ruler. By 1439, Frederick had become the undisputed head of the Habsburg dynasty.

Frederick was the cousin of late King Albert II, and was elected as King of Germany in 1440. He travelled to Italy in 1452 to receive his bride and be crowned Holy Roman Emperor. He was unsuccessful in being crowned King of Italy however, and was the last emperor to be crowned in Rome. Frederick was not able to gain control over Bohemia and Hungary, losing the Bohemian-Hungarian War and the Austrian-Hungarian War.

Frederick ultimately prevailed against his rivals through patience and cunning, outliving his opponents and then often inheriting their lands. He also gained lands and increased the influence of the Habsburgs through political marriages, giving rise to the saying 'Let others wage wars, but you, happy Austria, shall marry'. Frederick eventually died in 1493, aged 77, bleeding to death after having his infected left leg amputated.