| Conflict: | Battle of Ruona–Salmi |
| Partof: | the Finnish War |
| Date: | 1–2 September 1808 |
| Place: | Ruona and Salmi, Kuortane, Finland |
| Combatant1: | Sweden |
| Combatant2: | Russian Empire |
| Commander1: | Wilhelm Mauritz Klingspor Carl Johan Adlercreutz |
| Commander2: | Nikolay Mikhailovich Kamensky |
| Strength1: | Swedish accounts: 4,700–5,500 (3,400–3,500 engaged) Russian accounts: 8,000–12,000 (including 5,000 militia) 30 guns |
| Strength2: | Russian accounts: 9,000–11,000 (7,000 engaged) 58 guns |
| Casualties1: | Swedish accounts: 680–900 Russian accounts: 1,000–1,500 |
| Casualties2: | Russian accounts: 845–1,000 Swedish accounts: 1,200 |
The battle of Ruona–Salmi or the battle of Kuortane was fought between Swedish and Russian troops on 1–2 September 1808 at Ruona and Salmi, Kuortane. The Swedish army was led by Wilhelm Mauritz Klingspor with 4,700, 5,000, or 5,500 men under his command (according to Russian sources, there were 8,000 Swedes or 7,000 regular soldiers and 5,000 irregular) against the Russian army of between 9,000 and 11,000 men under the command of Nikolay Kamensky. The battle turned up to be a major engagement in the war where fierce artillery fire occurred from both sides. Kamensky, advancing from Alanus, beat back the Swedish barriers and on 31 August approached the Swedish army's position near Kuortane.
Kamensky, having sent detachments under the command of Colonel Vlastov and Major general Kazachkovsky to bypass the enemy's flanks, attacked the Swedish troops on September 1 from the front by the vanguard of Russian troops under the command of Colonel Kulnev, and then by the detachment of Major general Raevsky. Despite the fierce and stubborn fight, which was held with varying success, the Swedes could not be pushed out from their positions. Meanwhile, detachments of Vlastov and Kazachkovsky bypassed the Swedish position and Klingspor, fearing being surrounded, in the night of September 2 retreated to the rear off Salmi village. In the morning Kulnev's 4,000 strong detachment defeated the Swedish rearguard and attacked the main Swedish positions from the front, while Kazachkovsky's detachment attacked from the rear. The enemy, pursued by Russian hussars, retreated in disarray to the north-west towards the town of Vaasa, unable to withstand the assault.
The Swedes, who were in a well-fortified position, lost 170 killed, 400 wounded and 110 captured according to the reports of regimental losses, in addition to more than 300 men who had fallen ill. Other Swedish sources gives 900 losses. Russian assessment suggests that Swedes lost up to 1,500 men. The Russians lost 128 killed, 648 wounded and 51 captured (excluding 18 officers), according to their own estimates. According to Russian general, the losses reached almost 2,000 in total, with an equal amount on both sides. This battle is considered one of the turning points in the Finnish War along with the battle of Oravais.