Alexander Georg Rudolf Bauer (11 February 1889 – 28 November 1953) was a German-born painter who was involved in the avant-garde group Der Sturm in Berlin, and whose work would become central to the non-objective art collection of Solomon R. Guggenheim.

Born in Lindenwald, County of Wirsitz near Bromberg, Province of Posen, Kingdom of Prussia, to middle-class parents, Bauer's family moved to Berlin, Brandenburg, in his youth.

That same year he met Herwarth Walden, who had just founded the magazine Der Sturm and the affiliated gallery.

In 1920 Katherine Sophie Dreier, the preeminent collector and co-founder of the Société Anonyme, with Marcel Duchamp and Man Ray, visited Berlin and bought several works by Bauer including the oil Andante V (now in the permanent collection of the Yale University Art Gallery).

She would later write in 1949 that Bauer's paintings "were very beautiful and subtle in color and helped to introduce abstract art to the people.

Bauer remained in Berlin, province of Brandenburg, Free State of Prussia, in the 1920s and continued to make both abstract, or as the movement came to be known, "non-objective" art [a translation of the German gegenstandslos], as well as figurative work to support himself.

Rebay showed Guggenheim non-objective art by Bauer and Kandinsky, and he decided to start a collection of the work.

In 1930 Solomon Guggenheim and his wife, Irene, traveled with Rebay to Germany to meet Bauer and Kandinsky.

By this point, Bauer's work had moved from lyrical to geometric abstraction, which would dominate the rest of his artistic career.

Upon his arrest Bauer was held in a Gestapo prison for several months, as Rebay and Guggenheim worked to free him.

Bauer's work Orange Accent was featured on the invitation to the opening exhibition titled The Art of Tomorrow.

Bauer lived with Rebay for a few months before moving to one of Guggenheim's homes in Deal, Monmouth County, New Jersey, an upscale and beautiful but isolated coastal town.

Within a couple of years of Solomon's death the trustees abandoned Guggenheim's original vision for the collection.

The newly renamed Solomon R. Guggenheim Museum opened in 1959 without a single work of Bauer's on its walls.

In 2008, Grace and Michael Productions released a video-biography entitled Betrayal: The Life and Art of Rudolf Bauer.