The Diocese of Włocławek (Latin: Dioecesis Vladislaviensis) is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Poland.

It is a suffragan in the ecclesiastical province of the Metropolitan Archdiocese of Gniezno.

The bishops' seat is Włocławek Cathedral, also a minor basilica: Bazylika Katedralna Wniebowzięcia NMP in the city of Włocławek, in Kujawsko-Pomorskie.

The diocese has two more Minor Basilicas: The diocese is currently headed by Bishop Krzysztof Jakub Wętkowski, appointed in 2021.

As of 2022, it pastorally served 748,506 Catholics (98.7% of 758,348 total) on 8,824 km² in 233 parishes and 126 missions with 566 priests (460 diocesan, 106 religious), 463 lay religious (148 brothers, 315 sisters) and 24 seminarians.