Cosmo Nelson Innes FRSE (9 September 1798 – 31 July 1874) was a Scottish advocate, judge, historian and antiquary.
He served as Advocate-Depute, Sheriff of Elginshire, and Principal Clerk of Session.
He was a skilled decipherer of ancient Scottish records and helped to compile, edit and index Acts of the Scottish Parliament 1124–1707.
He was said to be tall, handsome but shy.
He was accused of being a Catholic sympathiser whilst it remained illegal, and joined the newly created Scottish Episcopal Church, close in practice to the Catholic Church.
Dean Ramsay, head of the Episcopal Church, was one of his friends.