Otto Martin Torell (5 June 1828 – 11 September 1900) was a Swedish naturalist and geologist. He was born in Varberg, Sweden on 5 June 1828. He was educated at Lund University for the medical profession, but became interested in zoological and geological studies, and being of independent means he devoted himself to science.
He gave his attention first especially to the invertebrate fauna and the physical changes of and recent times. In 1850 he applied Louis Agassiz's theory on ice ages to explain his observations of arctic molluscs on the coast of Sweden. From 1856 to 1859 he studied the glacial phenomena of Switzerland, Iceland, Spitzbergen and Greenland, and in 1861 made the first of two Arctic expeditions to the Polar sea in company with Adolf Erik Nordenskiöld. In 1865 he visited the Netherlands to investigate the strange rock formations and to explore the possibility of answering the prize contest set up by the Hollandsche Maatschappij der Wetenschappen since 1841 with the theme "What is to be thought of Agassiz's discovery that glacial moraines occur in Northern Europe far from present glaciers?". Since 1861 the question was broadened to include the question where the hondsrug rocks came from, and in 1867 Torell sent in a proposal to declare the rocks were transported by glaciers and was awarded the prize (a gold medal worth 400 guilders and cash to the amount of 150 guilders) but he never collected it, to the great frustration of the Haarlem Society's secretary, who sent him letters requesting his manuscript for publication. The 300 page manuscript was finally sent after Torell's death by the Swedish Geological survey, of which he had become director. His widow was awarded the prize posthumously.