Albi Cathedral, formally the Cathedral of Saint Cecilia (French: Cathédrale Sainte-Cécile d'Albi), is the most important religious building in Albi, southern France, and the seat of the Archbishop of Albi (in full, Albi-Castres-Lavaur). First built as a fortress begun in 1287 and under construction for 200 years, it is claimed to be the largest brick building in the world.

In 2010 the cathedral was designated a UNESCO World Heritage Site.