Spanish Fort or Old Spanish Fort may refer to:
The Spanish Fort in Colonia, the capital of Yap State in the Federated States of Micronesia, is a historic seat of power on the island of Yap. Only foundational remnants of the 19th-century Spanish fortification survive, on a property now occupied by the local hospital. The site was also where German and Japanese administrators had their headquarters during their respective periods of administration in the decades of the 20th century before World War II. The foundation was built of stone and cement, and is still accessible via its original steps.
The fort's remains were listed on the United States National Register of Historic Places in 1976, a time when Yap and the other Caroline Islands were part of the US-administered Trust Territory of the Pacific Islands.
A Spanish military fort was constructed and occupied in 1819 near Sangre de Cristo Pass in the present U.S. State of Colorado to protect the Spanish colony of Santa Fe de Nuevo México from a possible invasion from the United States. The fort was the only Spanish settlement in present-day Colorado. The site of this fort is known today as the Spanish Fort.
When René-Robert Cavelier, Sieur de La Salle, claimed the Mississippi River and its entire drainage basin for Louis XIV of France in 1682, he was unaware that the southwestern reaches of the basin extended into territory claimed by Charles II of Spain for the New Spain colony of Santa Fe de Nuevo Méjico. French and Spanish traders first encountered one another in 1739 along the Arkansas River. The conflicting claims of France and Spain to the upper Arkansas River basin were resolved in 1762 when Louis XV of France transferred the French colony of La Louisiane to Charles III of Spain with the secret Treaty of Fontainebleau.