Berengaria of León (1204 – 12 April 1237) was the third wife but only empress consort of John of Brienne, Latin Emperor of Constantinople.
According to the chronicle of Alberic of Trois-Fontaines, Berengaria was a daughter of Alfonso IX of León and Berengaria of Castile. She was a younger sister of Ferdinand III of Castile and Alfonso of Molina.
In 1217, Berengaria's brother Ferdinand III had inherited the throne of the Kingdom of Castile through abdication of their mother.
In 1223, John of Brienne, aged 53, visited Santiago de Compostela, as a supposed pilgrim. He was by then twice a widower. As a consequence of his visit to Santiago de Compostela, Alfonso IX invited him to marry his daughter Sancha and, presumably, through her inherit the Leonese throne. However Berengaria of Castile, a long time divorced and an inheritor in her own right of the Castilian throne, main advisor of her son Ferdinand III, offered one of her own daughters to John instead.
Aging John chose Berengaria of León, from Alfonso's second marriage. The marriage took place at Toledo in 1224.
In 1229, the throne of the Latin Empire had been inherited by Baldwin II of Courtenay, a twelve-year-old boy. The barons of the Empire decided to secure the safety of the Empire by appointing a regent-Emperor for Baldwin. They chose John who accepted the assignment as a sort of Senior Tutor. In April 1229, John was proclaimed regent at Perugia. They did not arrive at Constantinople until 1231, when John was officially crowned in his new city.
Baldwin II remained the junior co-emperor and only heir to the throne. By agreement, 12-year-old Baldwin had been betrothed to around 4- or 5-years-old Marie of Brienne, a daughter of John and Berengaria, since 19 April 1229 to firmly establish the dynastic alliance of the two co-emperors and the western land for Crusades also, Spain.