Harmar Denny (May 13, 1794 – January 29, 1852) was an American businessman and Anti-Masonic member of the U.S. House of Representatives from Pennsylvania.

[1] His father had served as adjutant to General Harmar during wars on the western frontier.

[2] Denny was elected as an Anti-Masonic candidate to the Twenty-first Congress to fill the vacancy caused by the resignation of William Wilkins.

After his term, he resumed the practice of law in Pittsburgh, and became a delegate to the Pennsylvania State Constitutional Convention in 1837.

New York State Senator Henry E. H. Brereton (1865–1957) was his grandson; Congressman Harmar D. Denny, Jr. (1886–1966) was his great-grandson.