Jimmy Ernst (born Hans-Ulrich Ernst) (June 24, 1920 - February 6, 1984) was an American painter born in Germany.

He was the son of surrealist painter Max Ernst and Luise Straus. When he was just two years old, his parents divorced, Jimmy staying with his mother. He first visited his father in France in 1930, where he met many of the surrealists, including André Masson, Yves Tanguy, Salvador Dalí and Luis Buñuel.

In February 1933 the Ernst family emigrated to Paris on account of being suspected by the new Nazi regime. In June 1938 Jimmy set sail from Le Havre, eventually arriving in New York. There he met many European exiles and befriended the city's avant-garde. His efforts to transport his father away from Nazi-occupied France finally succeeded in 1941. His mother, however, was sent to Auschwitz concentration camp in 1944, which she did not survive.

Ernst became director of The Art of This Century Gallery in 1942. A year later he had his first one-person exhibition. During the late 1940s he became a member of the The Irascible Eighteen, a group of abstract painters who protested the Metropolitan Museum of Art's policy towards American painting of the 1940s and who posed for a famous picture in 1950; members of the group included: Willem de Kooning, Adolph Gottlieb, Ad Reinhardt, Hedda Sterne, Richard Pousette-Dart, William Baziotes, Jimmy Ernst, Jackson Pollock, James Brooks, Clyfford Still, Robert Motherwell, Bradley Walker Tomlin, Theodoros Stamos, Barnett Newman, and Mark Rothko. These artists are part of the New York School they were referred to as The Irascibles in an article featured in an issue of Life where the infamous Nina Leen photograph [1] was published.

In 1951 he was granted the post of an instructor at Department of Design, Brooklyn College. He moved to East Hampton in 1969. He also built a winter home in Florida in 1980.

Ernst married Edith Brody in January 1947 and had two children, Amy Louise (1953) and Eric Max (1956).

Awarded Guggenheim Fellowship in 1961 and an honorary degree by the Long Island University (Southampton College) in 1982. Also elected to the American Academy.

His memoirs, A Not-So-Still Life, were published shortly before his death.

His son Eric Ernst and his daughter Amy Ernst are both artists.