Buják Castle, Medieval castle ruins in Nógrád County, Hungary

Buják Castle is a ruined castle on a 310-metre wooded hill north of Buják village, in Nógrád County. Its core is the old tower, first mentioned in a charter in 1303. The Báthory family added an outer ring of walls in the mid-16th century, including the large northern round bastion built around 1551. Remains of a Turkish mosque's walls still stand in the castle.

The stronghold was built following the Mongol raids and first documented in 1303 as a defensive position. Turkish forces destroyed it in 1666 during their expansion into the region.

The name Buják may derive from the old Hungarian word bú, meaning sorrow, though sources do not confirm this. Visitors can still see the remains of the Turkish mosque walls inside the castle, a trace of the 17th-century Ottoman garrison. The site is now a ruin visited by hikers, not a monument with regular ceremonies.

The site is accessible via marked hiking trails that also connect to nearby viewpoints in the area. Sturdy footwear is essential due to the uneven terrain and forest paths.

Inside the castle, the remains of the walls of a Turkish mosque are still visible, a trace of the Ottoman garrison of 28 men recorded in the 1556-57 pay register. The fortress was blown up around 1666 and has been a ruin ever since.