Ivan Lönnberg (12 November 1891, Stockholm – 26 April 1918, Cachy) was a Swedish modernist painter, marathon runner, and war veteran.

In style he was close to the Swedish painters of his generation known as "De Unga [sv]"[1] ("The Young") which included Isaac Grünewald and Birger Simonsson.

He came to Paris in January 1914, where he became a part of a circle of Swedish painters on Montparnasse including Grünewald, Einar Jolin, and Eric Detthow [sv].

While serving in Paris, he met artist Lena Börjeson and they started dating.

[2] He was mortally wounded by a shot in his left eye at the Western Front in 1918, the year the war ended.