The Castle of Guimarães () is the principal medieval castle in the municipality Guimarães, in the northern region of Portugal. It was built under the orders of Mumadona Dias in the 10th century to defend the monastery from attacks by Moors and Norsemen.
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).
History
thumb|left|235px|An 1863 engraving of the battlements and keep at Guimarães
Early history
thumb|235px|Photo of the Castle of Guimarães, 1845
Emblematic of the medieval Portuguese castle, Guimarães is associated with the origins of the Portuguese nation. Yet, the phases and organization involved in its construction, from the 10th century onwards is very deficient, with many of its present structure resulting from its reconstruction in the second half of the 13th century.