Adelphopoiesis, or "adelphopoiia" from the Greek ἀδελφοποίησις, derived from ἀδελφός (adelphos) "brother" and ποιώῶ (poio) "I make", literally "brother-making" is a ceremony practiced at one time by various Christian churches to unite together two people of the same sex (normally men). It is documented by the historian John Boswell in his book Same-sex unions in pre-modern Europe, also published as The marriage of likeness. The ceremony was mainly practised by the Eastern Orthodox church - Boswell gives text and translation for a number of versions of this ceremony in Greek, and translation only for a number of Slavonic versions.

The purpose of the adelphopoiesis ceremonies is controversial. Boswell maintained that they were celebrating romantic, indeed sexual unions between

Boswell comments on the lack of any equivalent in the Catholic church. However the British historian Alan Bray in his book The Friend, gives a Latin text and translation of a similar Roman Catholic rite from Croatia, entitled Ordo ad fratres faciendum, literally "Order for the making of brothers".

For alternative views, see and which maintain that this rite was used in many ways, to include between leaders of nations to make a permanent pact, as well as between religious brothers. This was a replacement for "blood brotherhood" which was forbidden by the church at the time.