Mathias Sigwardt Greve (17 September 1832 – 27 December 1912) was a Norwegian physician, best known as the director of Rikshospitalet from 1883 to 1911.
He was born in Bergen as a son of curate Arent Wittendorph Greve and Ulrike Eleonore Sigwardt.
He was a great-grandson of goldsmith Arent Greve and a grandson of bishop Mathias Sigwardt.
He worked as a physician in Kinn from 1857 to April 1858, in May 1858 he was hired at Nordre Trondhjems Amt Hospital in Namdalen.
He founded the sanatorium in Gausdal in 1878, was its manager until 1883 and chaired the association Den norske kurstedforening.