"In Dulci Jubilo/On Horseback" is a single by musician Mike Oldfield, released in 1975. The prominently festive single features an instrumental version of a Christmas carol, "In dulci jubilo", as well as the finale-song from Oldfield's Ommadawn album, "On Horseback".

Mike Oldfield's "In Dulci Jubilo" is an instrumental version of the German traditional Christmas carol of the same name, known best in England as "Good Christian Men Rejoice". Mike Oldfield had recorded another version of this song as the B-side to his previous single, "Don Alfonso", which did not chart, playing all instruments himself. Later, he felt a better version could be done, and re-recorded it in October 1975 at the Manor, but incorporating some of the previous version's backing tracks recorded November 1974 at the Beacon, his home studio.

The new version features Leslie Penning on two recorders and kortholt, Mike Oldfield on acoustic and electric guitars, piano and ARP string synthesiser, and William Murray on snare drum. Oldfield's decision to re-record the song proved to be a good move; it appeared in Christmas season playlists on radio across Europe, charting at number 4 in the UK, and is one of his most re-issued short songs. It also charted at number 7 in the Irish Singles Chart and at number 2 on the Dutch Top 40.

The song's authorship shown in the track listing below is how it appears on a recent compilation CD. Most editions from the 1970s and 1980s credit it to R. L. Pearsall, arr. Oldfield. Bach and Pearsall both wrote arrangements of it, but the song dates further back than either composer. Italian pressings of the single from 1975 credit it to J. S. Bach.

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