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.

Matsudaira Motoyasu (who would later come to be known as Tokugawa Ieyasu) 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 Motoyasu's siege of the castle, he and his men were not present at the Battle of Okehazama where Imagawa Yoshimoto was killed in Nobunaga's surprise assault.

In this siege, Motoyasu made good use of concentrated arquebus fire. Later during the siege, Sakuma Morishige the commander of the fortress, was killed by a bullet.