Margiris or Margis (died 1336) was a Duke of Samogitia, a medieval Lithuanian prince, mentioned in the chronicle of Wigand of Marburg as the heroic defender of Pilėnai in 1336. Not able to defend the castle against the siege of the Teutonic Knights, Margiris and other defenders decided to commit suicide, burning the castle and leaving no loot for the enemy.
Margiris held a high position in the Lithuanian society as evidenced by his duel with John of Luxemburg, King of Bohemia, who joined the Teutonic crusade against Lithuania and captured Medvėgalis in early 1329. After the rules of the duel were broken, Margiris had to pay a ransom. He did so with coins minted by Louis IV, Holy Roman Emperor stolen during the 1326 raid into Brandenburg. If Margiris was not from the ruling class, the King of Bohemia would consider it degrading to fight with him, and Margiris would not have a share of the spoils of war.
Regarding his family, chronicles mention only Margiris' son, who went to France after 1329 and whose wife was countess of Clermont of unknown name. Since the sources attest the high status and wealth of Margiris, historian Alvydas Nikžentaitis concluded that Margiris must have been a son of Butvydas and brother of Gediminas, Grand Duke of Lithuania.
- Family of Gediminas – probable family tree of Margiris