Sejr () is a Nordic name, most prevalent in Denmark. It derives from a Danish word meaning victory, triumph.
Notable people with this name include:
Surname Arne Sejr (1922–1998), Danish activist Emanuel Sejr (1891–1980), Danish author Epithet Valdemar Sejr (1170–1241), Danish king as Valdemar II of Denmark
Given name Sejr Volmer-Sørensen (1914–1982), Danish actor