The diocese of Leiria was created in 1545, the same year that Leiria was elevated to a city.

The Cathedral of Leiria is a sober mannerist building, whose construction started in 1559, following the demolition of the Church of São Martinho (between 1546 and 1549), and the opening of the new square. On May 22, 1545 the Diocese of Leiria was created and, in the same year, on June 13, Leiria was elevated to city. The architectural ensemble of the Sé de Leiria was classified as a National Monument in 2014.