Mark Simon Austin Tanner is a British Anglican bishop and academic. Since 2020, he has been the Bishop of Chester; he previously served as Bishop of Berwick, a suffragan bishop in the Diocese of Newcastle since his 2016 consecration as bishop; and from August 2011 until his consecration, he was the Warden of Cranmer Hall, Durham, a Church of England theological college.

The Bishop of Chester is the Ordinary of the Church of England Diocese of Chester in the Province of York.