Alfonso I (1073/1074 – 8 September 1134), called the Battler or the Warrior (Spanish: el Batallador), is the king of Aragon and Navarre from 1104 until his death in 1134.

He is the second son of King Sancho Ramírez and successor of his brother Peter I.

With his marriage to Urraca, queen regnant of Castile and León, in 1109, he begins to use, with some justification, the grandiose title Emperor of Spain, formerly employed by his father-in-law, Alfonso VI.

Alfonso the Battler earns his sobriquet in the Reconquista.

He wins his greatest military successes in the middle Ebro, where he conquers Zaragoza in 1118 and takes Ejea, Tudela, Calatayud, Borja, Tarazona, Daroca, and Monreal del Campo.

He dies in September 1134 after an unsuccessful battle with the Muslims at the Battle of Fraga.