The Dicastery for Promoting Christian Unity, previously named the Pontifical Council for Promoting Christian Unity (PCPCU), is a dicastery within the Holy See whose origins are associated with the Second Vatican Council which met intermittently from 1962 to 1965.

Pope John XXIII wanted the Catholic Church to engage in the contemporary ecumenical movement. He established a Secretariat for Promoting Christian Unity (SPCU) on 5 June 1960 as one of the preparatory commissions for the council, and appointed Cardinal Augustin Bea as its first president. The secretariat invited other churches and world communions to send observers to the council.

The Secretariat for Promoting Christian Unity prepared and presented a number of documents to the council:

Following the council, in 1966 Pope Paul VI confirmed the Secretariat for Promoting Christian Unity as a permanent dicastery of the Holy See.

In the apostolic constitution Pastor bonus (28 June 1988), Pope John Paul II renamed the secretariat the Pontifical Council for Promoting Christian Unity.

The PCPCU has two sections dealing with:

The dicastery has a twofold role:

Since its creation, it has also established a cordial cooperation with the World Council of Churches (WCC). Twelve Catholic theologians have been members of the WCC's Faith and Order Commission since 1968.