The Siege of Marune(丸根砦の戦い?) was a battle during the Sengoku period (16th century) of Japan.
Marune was a frontier fortress in the possession of Oda Nobunaga. Tokugawa Ieyasu, who was at the time a forced retainer of the Imagawa, captured the fortress as part of the Imagawa advance that led to the fateful Battle of Okehazama in 1560. Throughout Ieyasu's siege of this castle, he made good use of concentrated arquebus fire. During the siege Sakuma Morishige, the commander of the fortress, was killed by a bullet.