Fortress of Justinian, Byzantine fortress in Tirana, Albania.

The Fortress of Justinian, known locally as Kalaja e Tiranës, is a Byzantine-era castle in central Tirana. Above ground, only a 6-metre Ottoman-era wall covered in vines remains, with three known towers. The wall foundations were recently uncovered and incorporated into the pedestrianised Murat Toptani Street. Inside the former walls stand restaurants, hotels and cultural institutions.

Built before 1300 during the Byzantine period, the fortress was constructed at a key point where major trade routes crossed. This location influenced how Tirana developed over time as an urban center.

The name Tirana may derive from Tyranna, the form recorded by Barleti in 1505, though the toponym is still debated. Inside the walls stand two houses built after 1814 by the Toptani family, one for living and one for receptions. Since December 2018 a traditional bazaar has occupied the grounds, with craft workshops and restaurants serving Albanian dishes.

The fortress grounds sit between Murat Toptani Street and the Albanian Parliament, with the National Gallery of Arts and the Academy of Sciences on the same block. The surviving Ottoman wall and the uncovered foundations along the pedestrian street can be seen from outside at any time; the bazaar lanes and courtyards inside are entered on foot.

The wall foundations uncovered during recent work were declared a cultural monument in their own right on 15 May 2008, separately from the castle's 1973 listing. They now form part of the paved surface of Murat Toptani Street, so pedestrians walk directly over the excavated line of the old fortification.