The Diocese of Saint-Denis in Île-de-France (Latin: Dioecesis Sancti Dionysii in Francia; French: Diocèse de Saint-Denis-en-France) is a Latin diocese of the Catholic Church in France.

Erected in 1966 by Pope Paul VI, the diocese was split off from the Archdiocese of Paris and the Diocese of Versailles.

Its territory comprises the department of Seine-Saint-Denis.

As of 2011, the diocese remains a suffragan of the Archdiocese of Paris.

This came after a visit from Mgr Pascal Delannoy to the Archdiocese of Owando in July 2020.