Peter Waage (29 June 1833 – 13 January 1900) was a Norwegian chemist and professor of chemistry at the University of Kristiania. Along with his brother-in-law Cato Maximilian Guldberg, he co-discovered and developed the law of mass action between 1864 and 1879.^{[1] [2]}

He grew up on the island of Hidra in Vest-Agder, Norway. He was the son of Peder Pedersen Waage (1796–1872) and Regine Lovise Wathne (1802–72). He attended the Bergen Cathedral School and studied chemistry and mineralogy at the University of Kristiania (now University of Oslo) under Adolph Strecker. In 1858, he received the Crown Prince's gold medal (Kronprinsens gullmedalje) for work on the development of a theory of oxygen-containing acid radicals. He became a cand.real. in 1859. He subsequently traveled to France and Germany, where he studied for two years including time spent with Robert Bunsen in Heidelberg. ^{[3] [4]}

In 1861, Waage was made an associate professor and in 1866 he was appointed professor of chemistry at the University of Kristiania. He remained a professor at the University over 30 years. He was also chairman of the Norwegian Polytechnic Society from 1868 to 1869, and the first chairman of the Norwegian branch of the YMCA when it was established in 1880.^{[4] [5]}

He was married twice. In 1862, he married Johanne Christiane Tandberg Riddervold (1838- 1869), daughter of Hans Riddervold (1795-1876) and Anne Marie Bull (1804-70). Following the death of his first wife, he was married in 1870 with Mathilde Sofie Guldberg (1845-1907), sister of Cato Guldberg. ^[6]