Ut unum sint (Latin: 'That they may be one') is an encyclical on ecumenism by Pope John Paul II of 25 May 1995.

It was one of 14 encyclicals he issued, and Cardinal Georges Cottier, Theologian Emeritus of the Pontifical Household, was influential in its drafting.

In this groundbreaking exercise of the papal magisterium, Pope John Paul affirmed that the ecumenical commitment made at Vatican II was irreversible.

In paragraph 79, five subjects are noted to be "in need of fuller study before a true consensus of faith can be achieved": After an introduction, the encyclical's three chapters are entitled: These sections are followed by an exhortation calling on "everyone to renew their commitment to work for full and visible communion".

The two Codes of Canon Law include among the responsibilities of the Bishop that of promoting the unity of all Christians by supporting all activities or initiatives undertaken for this purpose, in the awareness that the Church has this obligation from the will of Christ himself.