Fet-Mats or Fat Mats (born Mats Israelsson; died 1677) was a natural mummy found in Sweden in 1719.
In 1719, miners in the Falun copper mine found an intact dead body in a water-filled, long-unused tunnel. When the body was put on display, it was identified by his former fiancée, Margaret Olsdotter, as Fet-Mats Israelsson, who had disappeared 42 years earlier.