Hume Blake Cronyn Sr. (28 August 1864 – 19 June 1933) was a Canadian politician and lawyer.

Born in London, Canada West, the son of Verschoyle Cronyn (who was the son of Benjamin Cronyn) and Sophia Eliza Blake (who was the daughter of William Hume Blake), Cronyn was educated at Dr. Tassie's grammar school in Galt, Ontario and at the University of Toronto where he received a Bachelor of Arts degree and a Bachelor of Law degree in 1889.

In 1907 he was appointed general manager of The Huron and Erie Mortgage Corporation.

[1] While at the University of Toronto he enlisted in The Queen's Own Rifles of Canada and served during the North-West Rebellion of 1885 and fought in the Battle of Cut Knife.

[citation needed] The Hume Cronyn Memorial Observatory at The University of Western Ontario was built in his memory by his widow Frances Amelia Cronyn (née Labatt).