Gundomad (Latin: Gundomadus; ? - 357 AD) or Gundomar, was an Alemannic petty king in the area around Breisgau, Germany in the 4th century. The Roman historian Ammianus Marcellinus reports that Gundomad, together with his brother Vadomarius, in 354 concluded a peace treaty at Augst after having been defeated in battle by emperor Constantius II. In 357, Gundomad was killed by his own people for having been to loyal to the Romans. They then made an uprising against emperor Julian.