Karl Heilmayer was a German landscape painter.

Heilmayer was born as the son of the royal court actor and landscape painter Emil Heilmayr. On November 6, 1843, he began his studies at the Royal Academy of Arts in Munich, but broke it off prematurely and continued his education as an autodidac .

Heilmayer remained active in Munich and mainly painted fog and moonlight landscapes. In his search for picturesque areas, he went on study trips to Upper Bavaria, Italy and South Tyrol, among others. He also visited Belgium, France and northern Germany.

Heilmayer displayed his works at exhibitions in Munich, Berlin, Dresden and Vienna.