Mathiasen is a Danish-Norwegian patronymic surname meaning "son of Mathias" (equivalent of the Biblical Μαθθαιος, cf. English Matthew). Several spelling variants are used, including Matthiasen and Matthiassen. A similar diversity of forms exist for the parallel given name Mathies/Mathis. Though not a hard and fast rule, generally spellings with a single s are Danish and a double ss are Norwegian. There are several people with the surname Mathiasen:
Jakob Mathiasen, Danish athlete Dwight Mathiasen (born 1963), Canadian ice hockey player Dennis Mathiasen (born 1981), Danish handball players
Matthiasen may refer to: Niels Matthiasen, Danish politician
Mathiassen may refer to: Therkel Mathiassen (1892–1967), Danish archaeologist
See also Matthiessen Mathiesen