Gundemar was a Visigothic King of Hispania, Septimania and Galicia (610–612).
Gundemar continued a policy of amity with Clotaire II of Neustria and Theodobert II of Austrasia. To this end, he sent grand sums of money to support their cause against their relative (cousin and brother, respectively) Theuderic II of Burgundy. At other times, he demonstrated a politic of hostility against Brunhilda.
According to Isidore of Seville, Gundemar made one expedition against the Basques, then besieged the Byzantines in the next. He died a natural death in Toledo, probably in February or March 612. The Chronica Regum Visigotthorum records that Gundemar reigned for one year, ten months and 14 days. He was succeeded by Sisebut.