The Mariandyni (Μαριανδυνοί, Μαριανδηνοί, or Μαρυανδυνοί) were an ancient tribe in the north-east of Bithynia. Their country was called Mariandynia (Μαριανδυνία, Stephanus of Byzantium s. v.) and Pliny speaks of a Sinus Mariandynus ("Mariandynian Gulf") on their coast. Greek myths have Mariandynus as their presumed eponymous hero.

The Mariandyni (Μαριανδυνοί, Μαριανδηνοί, or Μαρυανδυνοί) were an ancient tribe in the north-east of Bithynia. Their country was called Mariandynia (Μαριανδυνία, Stephanus of Byzantium s. v.) and Pliny speaks of a Sinus Mariandynus ("Mariandynian Gulf") on their coast. Greek myths have Mariandynus as their presumed eponymous hero.