Sir Thomas Frankland Lewis, 1st Baronet (14 May 1780 – 22 January 1855) was a British Poor Law Commissioner and moderate Tory MP.
Lewis was the son of John Lewis and Anne Frankland, daughter of Sir Thomas Frankland, 5th Baronet. Born in Great Ormond Street, London, he was educated at Eton College, and attended Christ Church, Oxford without taking a degree. His father died in 1797.
Lewis was an improving landlord of the family estates in Radnorshire, and was appointed High Sheriff of Radnorshire for 1804–05. He was ambitious to enter national politics as a Member of Parliament, which he did in 1812 as a follower of Lord Bulkeley, at Beaumaris.
Lewis was an MP for most years between 1812 and 1855, for Ennis (1826–1828), for Radnorshire (1828–1834) and for Radnor Boroughs (1847–1855). Initially he was known as a Grenvillite; while he supported the landowner and agricultural interest, his sympathy with Catholic emancipation made him unacceptable to the Tory ministry. From 1821 onwards he took the advice of Lord Grenville to establish himself by means of public commission work.
He was elected a Fellow of the Royal Society in 1820.