Thomas Kelsey (died c. 1680) rose from obscurity as a "London tradesman" to become an important figure in the government of Oliver Cromwell. Kelsey enlisted in the New Model Army and fought on the side of Parliament during the English Civil War, displaying a zeal that led him to become a major-general in 1645. He became a lieutenant-colonel in Colonel Ingoldsby's regiment from 1646. After the war he was elected as Deputy-Governor of Oxford, and in 1651 he was further appointed a lieutenant of Dover Castle.