Alpha Aquarii (α Aqr / α Aquarii) is a star in the constellation Aquarius. It also has the traditional names Sadalmelik, which derives from an Arabic expression سعد الملك sacd al-malik/mulk meaning "Luck of the king/kinghood", as well as Rucbah, which it shares with Delta Cassiopeiae. It is only one of two stars with ancient proper names to lie within a degree of the celestial equator.