Bihor, Medieval fortress in Târgu Neamț, Romania.

Bihor is a medieval fortification perched on Timus Rock in Târgu Neamț, Romania, with walls more than three meters thick made from river stones and green sandstone. The structure rises above the town and still displays its original polygonal layout with solid towers at the corners.

Built at the end of the 14th century under Prince Petru II (1375–1391), the fortress was first documented on 2 February 1395, when Sigismund of Luxembourg's Hungarian troops besieged it. In 1476 it withstood the Ottoman siege of Mehmed the Conqueror. It was destroyed in 1718 on the order of Mihai Racoviță.

The name Neamț is Slavic and Romanian for "German", and historians once linked it to Teutonic Knights supposedly building a castrum here between 1211 and 1225; archaeology found no fortification before Peter II's reign, and the name probably comes from the 14th-century Neamț Monastery. In the prison room four mannequins in chains recreate the fate of wrongdoers.

Access involves a steep path that climbs from the center of Târgu Neamț up to the rock, requiring sturdy footwear. The site lies near National Road DN15 and can also be reached by public transport from the town's railway station.

The stronghold withstood a siege by Mehmed II in 1476 because Ștefan cel Mare had installed artillery platforms and reinforced defense lines beforehand. These improvements made the structure one of the few places in the region able to resist Ottoman assaults.