Otto Bruenauer was an Austrian painter.

Otto Bruenauer attended four high school classes and graduated from the Vienna Commercial School. Against the wishes of his father, who had intended for him a position in his commercial business, he applied to the Academy of Fine Arts in Vienna. There he studied from 1900 to 1903 with Christian Griepenkerl and then at the Academy of Fine Arts in Munich with Heinrich Knirr.

After his studies, Bruenauer continued to live in Munich, but was also active in the Viennese art scene. In 1906 he successfully exhibited his painting Lady in Pink at the Spring Exhibition of the Vienna Secession. From 1907 to 1910 he was a member of the Vienna Hagenbund and took part in its exhibitions. He then belonged to the Luitpold Group in Munich and exhibited with the Munich Secession.

Bruenauer mainly painted still lifes and interiors. Bruenauer died of appendicitis at the age of 34.