Oliver John Ruthven is a conductor and continuo player based in London. He began his musical career as a chorister at Westminster Abbey, and went on from there to Tonbridge School and the University of Manchester. He graduated from Manchester in 2006 with a 1st Class Honours Degree in Music.

In opera, Oliver John was Music Director of Hampstead Garden Opera from 2008 to 2017, conducting a huge variety of repertoire ranging from Monteverdi to Jonathan Dove via Handel, Mozart and Donizetti. He has worked for the Royal Opera, Opera North, The Grange Festival, Garsington Opera, and The Early Opera Company.

​Since 2010, Oliver John has worked with the Monteverdi Choir and English Baroque Soloists under the direction of John Eliot Gardiner. This has principally been as a continuo keyboard player, but he has also sung as a tenor in the choir, acted as assistant conductor on several tours, and produced a recording of renaissance and early Baroque polyphony, which was released in April 2019.

He is in much demand as a continuo player, working as harpsichordist and organist for the English Baroque Soloists under Gardiner, and as a founder member of Musica Poetica. He has also played with Stile Antico, The Academy of Ancient Music, The Hanover Band, His Majesty's Sackbuts & Cornets, the English Cornet & Sackbut Ensemble, and Solomon’s Knot.

As a choral conductor and accompanist, Oliver John has worked with the National Youth Choirs of Great Britain, the Hallé Youth Choir, the Brighton Early Music Festival, and the Orchestra of the Age of Enlightenment's education department.
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He has been conductor of the Morgan Stanley Choir since 2013.