Byron Diman (August 5, 1795 – August 1, 1865) was an American politician who served as the 18th Governor of Rhode Island.
Diman was born in Bristol, Rhode Island, on August 5, 1795. He worked in a counting-house for over two decades. He was then engaged in the whaling and mill businesses. He served in the Rhode Island Militia and later became Brigadier General. He became a member of the Rhode Island House of Representatives for many terms.
He became Lieutenant governor of Rhode Island for three years before winning election as the governor of Rhode Island. He was a Law and Order Party candidate. Although he did not win the majority of votes, he was selected as the governor of the state by the General Assembly. He held the governor's office from May 6, 1846, to May 4, 1847.