Birtvisi Fortress (Georgian: ბირთვისი) is a ruined medieval fortress located in Kvemo Kartli, Georgia, within the limestone cliffs of the Algeti River gorge. It lies within the Tetritsqaro Municipality, next to Algeti National Park, and southwest of Tbilisi. The site is about 30 kilometers from the borough of Manglisi, accessible via the village of Partskhisi, followed by a 7-kilometer hike eastward. The route is reachable by various types of transport.
Birtvisi is not a conventional fortress surrounded by uniform walls. It is a natural fortress covering around 1 square kilometer, strengthened by man-made walls and towers. The most prominent tower, Sheupovari ("Obstinate"), sits atop the highest rock in the area. The complex includes defensive structures, residential and agricultural buildings, and reservoirs, with many features still visible among the ruins.
The fortress is first recorded in 1038 as a possession taken from the Arab emir of Tbilisi by Georgian nobles Liparit, Duke of Kldekari, and Ivane Abazasdze. Birtvisi was known as an impregnable stronghold, controlling the strategic Algeti gorge. In 1403, it was captured by Timur, who bombarded the fortress with catapults and breached its defenses, leading to a brutal assault and execution of the surviving defenders. Following the partition of the Kingdom of Georgia in the 15th century, Birtvisi came under the Kingdom of Kartli and was held by the Baratashvili family.
