Amadeus Aba or Amade Aba (Hungarian: Aba Amadé; Slovak: Omodej Aba; ? – 5 September 1311) was a Hungarian oligarch in the Kingdom of Hungary who ruled de facto independently the northern and north-eastern counties of the kingdom (today parts of Hungary, Slovakia and Ukraine). He held the office of Palatine (nádor) several times (1288–1289, 1290–1291, 1291–1293, 1295–1296, 1297–1298, 1299–1300, 1302–1310), and he was also judge royal (országbíró) twice (1283–1285, 1289). He was assassinated at the south gate in the city of Kassa by Saxon burghers.