The Castle of Guimarães (Portuguese: Castelo de Guimarães), is the principal medieval castle in the municipality Guimarães, in the northern region of Portugal. It was ordered constructed by D. Mumadona Dias in the 10th century in order to defend its monastery from attacks by Moors and Norman.
The castle is a military fortification grounded primarily in the late Romanesque period, and elaborated during the early Gothic epoch of Portuguese architecture. Its area is delineated by walls forming a pentagram, similar to a shield, that includes eight rectangular towers, military square and central keep. Originating in the foundations of a Roman structure, from the writings of Alfredo Guimarães, it was later elaborated on the French model, in its current the form of a shield, with reduced central yard and difficult accesses. It includes several Gothic characteristics, owing to its remodelling at the end of the 13th century, when the keep and residences were constructed (possibly over pre-existing structures).
The castle is located within the northern limits of the urban area of Guimarães, isolated on a small hill formed from granite, and encircled by a small forest park, accessed by several pedestrian trails. Alongside the southern tower is a bronze medallion of D. Afonso Henriques, over a large rock. In the vicinity, on the hillside, is the Romanesque church of São Miguel do Castelo and the Palace of the Dukes of Braganza and some sections of wall that surrounded the city, and that were originally integrated into the castle.