The son of the artist Phillip Fischer, Paul Gustave Fischer was born in Copenhagen into a Polish Jewish family, and was part of the fourth generation of this family to live in Denmark.
He began to paint when he was still young, guided by his father. He became a pupil of C. Möller, but was formally educated in art for only a short time in his mid-teens when he spent two years at the Royal Academy of arts in 1876. His first breakthrough came in 1882 when he created illustrations for the magazine Ude og hjemme, after which he came into contact with young Danish naturalists. Though he began his career by depicting city life, he soon incorporated richer and lighter colors into his palette after a stay in Paris from 1891-1895. It was not long before Fischer gained fame as a painter of cities, not just Copenhagen, but scenes from Scandinavia, Italy and Germany, reaching his zenith between 1890 and 1910. He benefited from contemporaries in Norway and Sweden, especially Carl Larsson. Around this time, he also painted bright, sunny bathing scenes, some with naked women, and developed an interest in posters, inspired by Théophile Steinlen and Henri de Toulouse-Lautrec, and also worked with illustrations for children’s books. Besides Paris, Fischer traveled and worked in Germany from 1883-1909 and Italy from 1894-1922.
Fischer’s greatest triumph as an artist came when Denmark transferred the sovereignty of Norway back to the Norwegians, and he was awarded the royal commission by King Haakon of Norway to paint the event over the more prominent painter Laurits Tuxen.