Retziusfjellet is a mountain on Kongsøya in Kong Karls Land, Svalbard. It is named after Swedish physician Gustaf Retzius.[1] The mountain reaches a height of 320 meters, and is the highest point of Kongsøya.[2] It is located south of Hårfagrehaugen (304 m.a.s.l.), and northwest of Tordenskjoldberget.[1]