Mathiasen is a Danish-Norwegian patronymic surname meaning "son of Mathias" (equivalent of the Biblical Μαθθαιος, cf.
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: Matthiasen may refer to: Mathiassen may refer to: