The Battle of Lier (Slaget ved Lier) was fought on 2 August 1814 between Sweden and the newly independent Norway as part of the Swedish-Norwegian War of 1814. The battle was the first major action of the war, and the Norwegian victory served as an important part to boost morale among the Norwegian troops. This was the second time during the Napoleonic Wars that a battle had taken place at Lier, the first was in 1808.