Rhain may refer to:
Wales Rhain ap Cadwgan or Cloten (fl. 8th century), King of Dyfed and Brycheiniog Rhain ap Maredudd (died c. 808), king of Rhainwg (Dyfed) Rhain the Irishman (Rhain Yscot) (fl. 11th-century), Irish pretender who held Dyfed
England RHAIN, former stage name of musician Rhian Teasdale
Slovenia Rhain or Rain is an ancient form of the former German name Rann of the town of Brežice and Brežice Castle (Schloss Rhain, or Schloss Rann)