Painter and printmaker Willi Geiger was born in Landshut, Germany in 1878. He attended the Munich Arts and Crafts School from 1898 to 1899 and the Munich Academy from 1903, under Franz von Stuck, alongside fellow artist Hans Purmann. He would later earn his teaching degree at the Munich Technical University. 

Earning the National Proze and the Schack Scholarship to study abroad, he traveled to Spain, Italy, and North Africa. He found particular inspiration in the works of Spanish artists Goya, Velasquez, and Greek artist El Greco, and after his return to Germany to work in Berlin he turned his attention to portrait painting, copying the works of these artists in order to instruct himself on their techniques. Among his first commissions was a portrait of the composer Hans Pfizer, which is said to reflect the influence of El Greco.

In 1914 he returned to Munich, taking a post as professor of painting at the School of Decorative Arts in Leipzig. He remained there until the late 1930s when the seizure of power by the Nazi's led to his dismissal. An outspoken anti-totalitarian, his work was deemed degenerate, especially his graphic work which often focused sympathetically on the lives of the poor and disenfranchised. He was forbidden to sell his work in Germany, essentially forcing the artist into retirement. He continued to paint, however, and after the war he offered a position at the College of Fine Arts in Munich, beginning in 1946. He continued to teach and exhibit in Munich until his death in 1971. 

Geiger was awarded the Villa Romana Prize for his work as a graphic designer in 1910; in 1951 he was awarded the Culture Prize of the City of Munich. 

Geiger's work can be found in private and public collections throughout the world.