Alonso de Reinoso (or Reynoso) (1518–1567) was a Spanish Conquistador in Honduras, Mexico, Peru and Chile. He was born in Torrijos Toledo, Spain in 1518. He was married to Catalina Flores de Riofrío before he came to the Americas in 1535.
He first disembarked in Cartagena de Indias in Colombia but soon moved on and fought for twelve years in Honduras and the Yucatán Peninsula with Pedro de Alvarado and Francisco de Montejo and was one of the first Alcaldes of the new city of Mérida. Leaving Mérida he went to fight in Peru for two years until he met Francisco de Villagra who was recruiting more men for Pedro de Valdivias campaign in Araucanía.
In 1551 he came to Chile with Francisco de Villagra. An experienced soldier he soon be became Corregidor of the city of Angol in 1554 after the death of Valdivia. Francisco de Villagra then appointed him as Maestro de Campo for his army in 1554. After fighting in the Battle of Marihueñu, he survived the defeat and evacuation of Concepcion. Returning to Santiago, he supported Villagra against the attempt of Francisco de Aguirre to become governor of Chile.