The Diocese of Aveiro (Latin: Dioecesis Aveirensis) is a Latin Church diocese of the Catholic Church in Portugal.

It has existed since 1938 when the historical dioceses of Coimbra, Porto, and Viseu were combined.

It is a suffragan of the archdiocese of Braga.

The bishop is António Manuel Moiteiro Ramos, appointed in 2014.

[2] The territory covers 1,537 km² and is divided into 101 parishes, grouped into 10 archipresbiterati, corresponding to the 10 municipalities of the district.