Diehl is a surname, and may refer to

David Diehl (b. 1980), American football player

August Diehl (b. 1976), German actor

Terry Diehl (b.1949), American professional golfer

Diehl BGT Defence GmbH & Ko KG, German arms manufacturer

John Diehl (b. 1950 or 1958), American character actor

William Diehl (1924–2006), American novelist and photojournalist

William J. Diehl (1845–1929), Mayor of Pittsburgh

Diehl Aerospace GmbH, German aerospace company

House of Diehl, New York-based fashion partnership

Diehl Mateer (b. 1928), American hardball squash player

Ella Diehl (b. Ella Karachkova), Russian badminton player

Diehl DM-41, military projectile

Arthur Diehl (1870–1929), English impressionist landscape artist

James Diehl (b. 1937), minister and general superintendent in the Church of the Nazarene

Philip Diehl (inventor) (1847–1913), inventor of the electric ceiling fan