Dom Nuno Álvares Pereira, O. Carm. (Portuguese pronunciation: [ˈnunu ˈaɫvɐɾɨʃ pɨˈɾɐjɾɐ]; June 24, 1360 – April 1, 1431), also spelled Nun'Álvares Pereira, was a Portuguese general of great success who had a decisive role in the 1383-1385 Crisis that assured Portugal's independence from Castile. He later became a mystic, was beatified by Pope Benedict XV in 1918 and was canonised by Pope Benedict XVI in 2009.

Nuno Álvares Pereira was born in Flor da Rosa, near Crato, central Portugal. His parents were Dom Álvaro Gonçalves Pereira, Prior of Crato and Iria Gonçalves do Carvalhal. His grandfather was Dom Gonçalo (Gonçalves) Pereira, 97th Archbishop of Braga (1326–1349). He descended from the oldest Portuguese and Galician nobility. At age 17, he married Leonor de Alvim, daughter of João Pires de Alvim and wife Branca Pires Coelho and childless widow of Vasco Gonçalves Barroso.

Nuno started a military career very early. He was in the army when he was only 13, in 1373, and helped stopping a Castilian invasion. However, according to his own words, his first military campaigns were no more than skirmishes on the borders of Portugal. He was an impetuous and brave young man who soon showed himself to be an excellent leader.