John Marsh (31 May 1752 – 31 October 1828) was an English gentleman, composer, diarist and writer born in Netherseal, Derbyshire, England.
Marsh lived in Dorking, Gosport, Romsey, Salisbury and Canterbury before settling in Chichester in 1787 until his death in 1828.
His style owes much to Handel and Corelli and it is close to other composers of the time, such as William Boyce.
Apart from the orchestral, ensemble, vocal and choral music, he also published many sets of organ voluntaries, totalling over 350 pieces, which are undated and, in which, quite unusually, he gives precise instructions for registration and dynamics.
During the twentieth century, his musical works lay in obscurity and he has only recently enjoyed a limited revival.
Marsh was a man of varied interests, and his 37 volumes of journals are among the most valuable sources of information on life and music in 18th-century England.