The Battle of Vsters (Swedish: Slaget om Vsters) was a battle in the Swedish War of Liberation that took place on Badelundasen, north of Vsters, Sweden on April 29, 1521. The Swedish troops, led by Gustav Vasa, defeated the Danish force, led by Didrik Slagheck, and conquered Vsters.

Gustav Vasa, who after going to Gstrikland and attempting to rally support for his rebellion, returned to Dalarna in early April and was informed of the victory in the Battle of Brunnbck Ferry. He decided to continue onwards to Vsters. His troops had on April 23 made camp by Romfartuna Church, where the army was mustered. On April 28 they broke up and marched to Vsters, not knowing that a peasant army attempting to take the city Kping two days earlier had been defeated by the forces of Dridrik Slagheck, who had now arrived in Vsters. Gustav Vasa arrived on April 29 and began preparing a siege. They were spotted by Slagheck's troops and attacked, but managed to force the attackers into retreat.

No major victory was won and the Danish forces remained in the city for a month, making more, if failed, sorties against the besieging Swedish troops. On May 20 the Danish left the city, leaving only a small force in Vsters Castle and shipping away the other troops. The castle held out until January 30, 1522, when attempts to aid the garrison by sea from Stockholm failed.

The Swedish War of Liberation (1521–23; Swedish: Befrielsekriget, lit. 'The Liberation War'), also known as Gustav Vasa's Rebellion and the Swedish War of Secession, was a rebellion and a civil war in which the nobleman Gustav Vasa successfully deposed King Christian II from the throne of Sweden, ending the Kalmar Union between Sweden, Norway, and Denmark.