Amadeus Aba or Amade Aba was a Hungarian oligarch in the Kingdom of Hungary who ruled de facto independently the northern and north-eastern counties of the kingdom. He held the office of Palatine several times, and he was also judge royal twice. He was assassinated at the south gate in the city of Kassa by Saxon burghers.

The Palatine of Hungary was the highest-ranking office in the Kingdom of Hungary from the beginning of the 11th century to 1848. Initially, Palatines were representatives of the monarchs, later the vice-regent (viceroy). In the early centuries of the kingdom, they were appointed by the king, and later were elected by the Diet of the Kingdom of Hungary. A Palatine's jurisdiction included only Hungary proper, in the Kingdom of Croatia until 1918 the ban held similar function as the highest office in the Kingdom, monarch's representative, commander of the royal army and viceroy.