Boroldai (or Burulday, Borolday), also known as Burundai, (Cyrillic: Боролдай) (died 1263) was a Mongol general of the mid 13th century.
He was probably from one of four tribes that Genghis Khan (1162–1227) assigned to his eldest son, Jochi: the Sanchi'ud (or Salji'ud), Keniges, Uushin, and Je'ured clans.
Serving under Jochi's successor and son, Batu Khan, Borolday's vanguard surprised and crushed the great army of Yuri II, the Grand Prince of Vladimir, at the battle of the Sit River in 1238.
After a very hard fight, Batu's army crushed the Hungarians and their allies, Croats and Templar Knights at Mohi on April 11, 1241.
After pillaging several villages and towns in Lithuania, Borolday returned to Galich and demanded Daniel assist him in his battle against the Poles.
His name appears in the opera The Legend of the Invisible City of Kitezh and the Maiden Fevroniya by Nikolai Rimsky-Korsakov, and in Mongolian fairy tales.