Peter Claussen (1804-1855) was a Danish natural history collector born in Copenhagen. His botanical collections are present in many European herbaria. He sold animal fossils to the British Museum and the Jardin des Plantes in France. He later had an article about the geology of Minas Gerais published through the L'Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique.
On account of fraud he emigrated to Brazil, and with Don Pedro I's army arrived in Rio de Janeiro. He at first enlisted as a common soldier and later lived as a peddler. During Argentine's Cisplatine War with Brazil between 1825-1828, he served as a spy. Later he lived as a merchant in the province of Cachoeira do Campo, in the State of Minas Gerais, becoming the owner of a farm in the northerly neighborhood of Curvelo, some days' journey north of Lagoa Santa.
On his great journey through the Brazilian countryside in 1833-35, he chanced to meet the Danish naturalist Peter Wilhelm Lund accompanied by the German botanist Ludwig Riedel in October 1834. Claussen had gone there under the name of 'Pedro Claudio Dinamarquez', and stayed on Lund's farm 'Porteirinho' for about a week. This meeting proved a turning point in both Lund's and Claussen's lives. On the farm were caves in the limestone hills, and these were exploited by the local people for fertilizer. Visits to these caves by Lund uncovered numerous fossil remains. The study of these linked Lund forever to inland Brazil. For commercial reasons Claussen's acquaintance with Lund turned him into a natural history collector, both of plants and fossil animals.