The Roman Catholic Diocese of Maasin (Lat: Dioecesis Maasinensis) is a diocese of the Latin Church of the Catholic Church in the Philippines, comprising the civil province of Southern Leyte and six municipalities from the fifth legislative district of Leyte.

On August 14, 1968, the Diocese of Maasin was canonically erected through an apostolic constitution with the incipit Dei Filium adorandum issued March 23, 1968 by Pope Paul VI.

[3] The population of Southern Leyte is made up mostly of Cebuano-speaking people because of its closeness, geographically, to Cebu and Bohol.

The Diocese of Maasin today has started to focus on the vision of the Second Plenary Council of the Philippines.

Apart from the usual ministerial and sacramental functions, the clergy has succeeded to penetrate the people's conscience with concern for other issues, such as reforestation, among others.

Thus the vision that was planted and took root when Pedro Valderrama celebrated the first Mass in the Philippines on March 21, 1521, has borne new fruit.