The "Sioni" Cathedral is a Georgian Orthodox cathedral located in Tbilisi. It was named after Mount Zion at Jerusalem following the medieval tradition of naming churches after places in the Kingdom of Israel. It is famous as the "Tbilisi Sioni" to distinguish it from some other churches in Georgia having the name Sioni.

The Sioni Cathedral has been the main Georgian Orthodox Cathedral and the seat of Catholicos-Patriarch of All Georgia until 2004 when the Holy Trinity Cathedral was consecrated.

The Tbilisi Sioni Cathedral is located in Sionis Kucha meaning Sioni Street, in downtown Tbilisi, fronting Mtkvari River. Initially built in the 6th-7th centuries, it has been destroyed by foreign invaders and reconstructed a few times. Currently the church is of a 13th-century version holding several changes from the 17th to 19th centuries.

Medieval Georgian annals indicates that King Vakhtang Gorgasali was the founder of the original church in the 5th century. A century later, Guaram, the prince in charge of Iberia, in c. 575 started constructing a new structure, which was brough to its final image by his successor Adarnase about in 639. The legend tells that both princes were buried in this church, but no trace of their raves has been found. This early version of the church was totally ceased to exist by Arabs, and later on was completely rebuilt by King David the Builder in 1112. The fundamental elements of the current structure come from this period. In 1226 it was considerably damaged, its dome was ruined by of Jalal ad Din Mingburnu.  It was then repaired, but in 1386 again damaged by Timur and repaired by King Alexander I. Another damage was caused in the 17th century during the Persian invasion.

The Sioni Cathedral is a typical sample of medieval Georgian architecture  with projecting polygonal apses in the east façade. The yellow tuff which was used to build the cathedral originates from Bolnisi (a town southwest of Tbilisi). The facades are explicit holding few decorations, despite the fact that there are bas-relief cross carvings and a lion that is chained on the western side and an angel and saints on the north.