The Oxford Inter-Collegiate Christian Union, usually known as OICCU (/ˈɔɪkjuː/ OY-kew), is the world's second oldest university Christian Union and is the University of Oxford's most prominent student Christian organisation. It was formed in 1879.

Due to the strength of the Oxford Movement and later the Oxford Groups (alternative Christian movements), evangelical Christians in Oxford have generally faced a more pluriform environment than in Cambridge, and OICCU has tended to follow the general lead of its Cambridge counterpart, the Cambridge Inter-Collegiate Christian Union (CICCU).

OICCU admits postgraduate students as well as undergraduates, although postgraduates are eligible only for associate membership, and their needs may be better served by the Oxford Graduate Christian Forum.

The OICCU vision is: Giving every student in Oxford University the chance to hear and respond to the Gospel of Jesus Christ

The three aims of OICCU are:

OICCU adopts the doctrinal basis of UCCF (Universities and Colleges Christian Fellowship), an evangelical Christian organisation with which OICCU is affiliated. The doctrinal basis contains what evangelicals perceive as the biblical foundations of Christianity. UCCF is in turn affiliated with the International Fellowship of Evangelical Students (IFES).

OICCU was modelled after the Cambridge Inter-Collegiate Christian Union (CICCU), founded two years earlier, but later incorporated a Daily Prayer Meeting established in Brasenose College in 1867. Like Wycliffe Hall (also 1877), it could be seen as a response to the University's abandonment of its previous officially Protestant position. The initial members included Francis Chavasse, subsequently Bishop of Liverpool and founder of St Peter's College.

OICCU was a founder member of the Student Christian Movement and followed its lead in liberalizing its doctrine. In 1914 OICCU, along with the rest of the University, suspended its activities.