Theodor Philipsen (10 June 1840 Copenhagen - 3 March 1920 Copenhagen) was a Danish painter. Philipsen has been considered an innovator of 19th century Danish art. He took Danish art into a new level of impressionism and naturalism. He was influenced by French art, this influence beginning in his first time in Paris from 1874–1876. He was impressed by the painters Théodore Rousseau, Constant Troyon, and perhaps Jean-François Millet. He made a close personal friendship with the French impressionist Paul Gauguin who was also an important source of inspiration for him. He traveled to many places in the world for inspiration including North Africa and Andalusia. His first impressionist principal work was Late Autumn Day in the Jægersborg Deer Park which he painted in 1886. The painting is currently in Statens Museum for Kunst. He participated in the exhibition Nordic and French Impressionists. Another one of his more famous paintings is An Avenue in Kastrup, which he painted in 1892. He was one of the most influential impressionist Danish painters of all time.A collection of Philipsen's works is kept at Kastrupgårdsamlingen in Copenhagen.