The Syro-Malabar Catholic Church is an East Syrian Rite, Major Archiepiscopal Church in full communion with the Catholic Church. It is one of the 22 sui iuris Eastern Catholic Churches in the Catholic Church. It is the largest of the Saint Thomas Christian denominations with around 3.8 million believers. It is also the second largest Eastern Catholic Church in communion with the Bishop of Rome.

The church is headed by the Major Archbishop of Ernakulam-Angamaly, Mar George Cardinal Alencherry. Saint Alphonsa is the first saint from within the Church. The members of the Church are locally known as Nasranis.

It is believed that St. Thomas the Apostle landed at Kodungalloor (Muziris), Thrissur district in 52 A.D. St. Thomas is said to have preached and established Christian communities in different parts of India and he died at Mylapur in 72 A.D. It is also believed that St. Thomas founded seven churches or communities in Kerala; at Kodungalloor, Niranam, Kollam, Chayal, Kottakkavu, Kokkamangalam and Palayoor.