Claim: Rouen Cathedral is a Roman Catholic church which is the largest Christian church with approximately 1.3 billion baptized Catholics worldwide as of 2018.
Evidence: Rouen Cathedral (French: Cathédrale primatiale Notre-Dame de l'Assomption de Rouen) is a Roman Catholic church in Rouen, Normandy, France. The Catholic Church, sometimes referred to as the Roman Catholic Church, is the largest Christian church, with approximately 1.3 billion baptised Catholics worldwide as of 2018.