The Castle of Vilar Maior (Portuguese: Castelo de Vilar Maior) is a well-preserved medieval castle located in the civil parish of Aldeia da Ribeira, Vilar Maior e Badamalos, in the municipality of Sabugal, Guarda district, Portugal.

Discoveries in 1956 that included a sword, some rock art (consisting of geometric designs) and axes, in the Quinta da Formiga and in Fraga, suggest a period of occupation dating from the Neolithic, late Bronze Age and Roman period. At about this time, from similar examples, it is presumed that a pre-Roman castro existed on the site. Around 60 A.D. Romans conquered the Lusitanian castro, but reconstructed and refortified the site. Fragments from tiles, ceramics and coins, in addition to vestiges of mosaics and Roman pavement, were discovered in and around the former castro.

In 1139, the settlement was taken by Leonese troops from the Moors and a castle reconstructed on the site. It eventually began to pertain to the Order of São João do Pereiro. A 1227 Latin document referred for the first time to the Vilar Maior, a toponymy that was associated with the early small colony; "vilar", which is a diminutive of "vila" (or town) referred to the site occupied by a group of one of two families.

In 1230, the site was reconquered by Leonoses forces from Portuguese troops. On 6 August 1232, a letter was issued by King D. Alfonso IV of León to encourage settlement in the region. But this was annulled by King D. Fernando II of León, who reintegrated Vilar Maior into the municipality of Sabugal. His successor was then responsible for the reconstruction of the castle in the intervening years.

Between 12th and 13th century, the location was easily defended by natural defenses, but with the advent of canons the site began to be considered vulnerable. By the second half of the 13th century, a new settlement letter was issued by King D. Alfonso X of Castile. By 1280, from an inscription, the urban perimeter wall ordered constructed by Alfonso X of Castile or, at least, the line that terminated at the Rua do Arco was concluded.

In 1296, the castle was conquered by forces loyal to King D. Dinis, at the time garrisoned by Leonese D. Sancho Peres de Ledesma. A foral (charter) was conceded on 27 November 1296. The castle, or at least the keep tower, was constructed by King Dinis, with the assistance of the Knights Templar. By 12 September 1297, the territory was integrated into the Portuguese kingdom, during the sequence of the Treaty of Alcanices.

Between 1367 and 1383 there were interventions in the castle under the initiative of D. Fernando, followed-up in 1398 by King D. John I. This work on the site, ultimately, led to the creation of the couto of Vilar Maior, which had attained a population of approximately 1000 residents by 1440. By the 1496 "Inquirição" (Inquiries), Vila Maior had reached a population of 234 residents.

On 1 January 1510, the towns foral was upgraded and new interventions in the castle were undertaken by King D. Manuel I. Designs by Duarte d'Armas observed that the citadel included a double line of walls. Yet, even in this interpretation there were ruins and a line of walls that encircled the keep tower. The second line of walls, identifiable by a barbican, improved the defense and protection of the entryway. The keep tower was covered in tile and was accessible by a stone staircase that parted from the courtyard to the second level doorway. The design also included scaffolding around the tower, permitting a better line of protection around the keep and improving its protection. The scaffold protected the archers and created the conditions for vertical vollies identical to the machicolations, making the castle's defense more complex. Alongside the bridge were remains of town walls, therefore suggesting a third line of defenses. Today there are remnants of this group in the staircase near the old municipal building, along the Rua da Costa, and within the Museum of Vilar Maior; a majority of these walls were destroyed to make way for the walls of the cemetery.