Castle of Alba, Losacino, Medieval castle in Losacino, Spain.

The castle of Alba stands on a hill above the Aliste River and the Retael stream, next to the village of Castillo de Alba in Losacino. Of the medieval fortress, some wall sections and a square keep with slightly pyramidal sides and arrow slits at the top remain. The Ricobayo dam has altered the surrounding landscape.

First documented in a 960 Sahagún diploma as "Alba Castello", the castle was probably revived on an older hillfort site under Alfonso III of Asturias. Fernando II of León enlarged it in the 12th century during wars with Portugal. Alfonso IX pledged it to the Templars in 1211 and restored it to them by the 1220 Concord of Villafáfila; the order held it until 1310. Portuguese forces took it in 1640.

The castle gave its name to the village of Castillo de Alba, which lies beside it in the municipality of Losacino. In 1459 Enrique IV granted Enrique Enríquez the title Count of Alba, making the fortress and the village the head of the counts' jurisdictional lordship of Alba de Aliste.

Visitors can reach the ruins by following a marked pathway that starts in Losacino and leads across open countryside to the hilltop. The exposed location makes visits more comfortable during milder months when weather conditions are more favorable.

The square keep with its slightly pyramidal profile and arrow slits high up dates from the Templar period, which lasted ninety years until 1310, when the commander Fray Gómez Pérez took refuge there after the order's expulsion from Castile. The castle passed to the Order of San Juan after the Templars were suppressed by the papal bull Vox in excelso in 1312.