Michael Sars (b.1809 d.1869) was a Norwegian theologian and biologist.

Sars was born in Bergen, Norway. He studied natural history and theology at Royal Frederick's University from 1823 and completed a degree in theology in 1828. For several years he taught at a number of different schools, firstly in Christiania and then in Bergen. In 1831 he was appointed vicar to Kinn on the Norwegian north west coast; eight years later he transferred to Manger, just north of Bergen. Finally, in 1854 he was named Professor of Zoology at the University where he remained for the rest of his life. He died in 1869. He was married to Maren Welhaven, sister of the epic poet, Johann Sebastian Welhaven, in 1831, and had 7 daughters and 7 sons.

Sars issued his first publication in 1829 (Contributions to the Natural History of Marine Animals); a second followed in 1835 (Descriptions and Observations etc.). He also issued two large-scale volumes under the title Fauna Littoralis Norvegiae. In all these publications Sars described the form of new taxa, a routine activity of scientists of the period, but he also described life-histories and reproductive cycles, food and feeding, behavior and geographical dispersal. The British zoologist, Edward Forbes, had issued a series of widely dispersed articles on biogeography, claiming that at depths greater than 300 fathoms, no animal life existed. Sars and his colleagues knew better and in a series of reports issued in various Norwegian journals, he documented the presence of a number of taxa in Norwegian fjords. As a result of one of his dredging expeditions, Sars described Rhizocrinus lofotensis, the first living stalked crinoid to be described. This find spurred academic interest in the deep sea and prompted the Challenger expedition and other similar ventures around the globe.

Michael Sars was one of the last great descriptive zoologists who catalogued organisms more or less equally successfully in all major animal groups. Sars also described fossils from various fossil beds in Norway and appears to have been keenly interested in all sorts of other issues. Sars was asked by the Norwegian Parliament to investigate the biology of Norwegian fisheries, such as the herring and cod fisheries. He had started these investigations by the time of his death, but most of them were completed and published posthumously by his son, Georg Sars.