Thomas Seymour, 1st Baron Seymour of Sudeley, KG (c. 1508-20 March 1549) was the brother of the English Queen Jane Seymour (the third wife of King Henry VIII) and uncle to King Edward VI. He was also the fourth husband of Catherine Parr who was the sixth and last wife of Henry VIII. 

Thomas was the son of Sir John Seymour and Margaret Wentworth. He grew up at Wulfhall in Wiltshire. He was the brother to Edward Seymour, Elizabeth Seymour and Jane Seymour.