Leonard Max Gumpel (23 April 1890 – 3 August 1965) was a Swedish building contractor and Olympic swimmer and water polo player.

[1] Gumpel was born in a rich family, and in 1906 was one of the founders and early sponsors of the Stockholm swimming club SK Neptun.

During World War II Gumpel was involved in espionage with his friend Eric Erickson.

With their help the allied powers obtained the exact locations of Germany's petroleum refineries and then bombed them.

He owned the motorboat Laila and the skerry cruiser La Liberté designed in 1934 by Erik Salander – both built at Kungsörs Båtvarv in Sweden.