The "Sioni" Cathedral of the Dormition (Georgian: სიონი (ტაძარი)) is a Georgian Orthodox cathedral in Tbilisi, the capital of Georgia. Following a medieval Georgian tradition of naming churches after particular places in the Holy Land, the Sioni Cathedral bears the name of Mount Zion at Jerusalem. It is commonly known as the "Tbilisi Sioni" to distinguish it from several other churches across Georgia bearing the name Sioni.
The Tbilisi Sioni Cathedral is situated in historic Sionis Kucha (Sioni Street) in downtown Tbilisi, with its eastern façade fronting the right embankment of the Mtkvari River. It was initially built in the 6th-7th centuries. Since then, it has been destroyed by foreign invaders and reconstructed several times. The current church is based on a 13th-century version with some changes from the 17th to 19th centuries. The Sioni Cathedral was the main Georgian Orthodox Cathedral and the seat of Catholicos-Patriarch of All Georgia until the Holy Trinity Cathedral was consecrated in 2004.