Alfonso III (4 November 1265 – 18 June 1291), called the Liberal (el Liberal) and the Free (also "the Frank", from el Franc), was king of Aragon and Valencia, and count of Barcelona (as Alfons II) from 1285 until his death.

Alfonso initially sought to maintain Aragonese control over Sicily by supporting the claims of his brother James II to the island.

However, he later retracted his support for his brother shortly before his death and instead tried to make peace with the Papal States and with France.

[1] His reign was marred by a constitutional struggle with the Aragonese nobles, which eventually culminated in the articles of the Union of Aragon – the so-called "Magna Carta of Aragon", which devolved several key royal powers into the hands of lesser nobles.

During his lifetime a dynastic marriage with Eleanor, daughter of King Edward I of England, was arranged.