Thomas Phinn (1814 – 31 October 1866) a British barrister and Liberal Party politician who held various positions in the Admiralty of the United Kingdom (the body governing the Royal Navy) in the mid-nineteenth century.
Born in Bath, Somerset, Phinn was educated at Eton College and Exeter College, Oxford. He read for the bar at the Inner Temple, being called in 1840. He was elected at the 1852 general election as Member of Parliament (MP) for Bath, but held that seat for only three years, until 1855. He was appointed Counsel to the Admiralty and Judge Advocate of the Fleet on 17 April 1854, and continued in that office until appointed Second Secretary to the Admiralty on 22 May 1855, a post which required his resignation from the House of Commons. He resigned from the Admiralty on 7 May 1857, but was re-appointed Counsel and Judge-Advocate on 12 November 1863, and held that post until his death on 31 October 1866, in London.