Åsunden, Lake in Västergötland, Sweden.

Åsunden is a large lake in Västergötland with multiple small islands scattered across its surface and a complex shoreline. The waterway connects to the Ätran river, which serves as one of its primary outflows.

The Battle of Bogesund was fought on the ice and shore of Åsunden on 19 January 1520. Christian II of Denmark defeated the Swedish regent Sten Sture the Younger, who was hit by a cannonball early in the fight; his knee shattered, he was placed in a sledge bound for Stockholm but died before the party arrived. The uprising army scattered in disorganised retreat, and Christian was crowned King of Sweden later that year.

Steam sloops ran on the lake from 1868, when Hedvig entered service; Limmared glassworks bought her in 1874 and added Bogesund and, in 1879, Helge, carrying goods and passengers between Ulricehamn and Karlsvik, where an ox-drawn rail line ran to the glassworks. From the 1950s motorboats have carried tourists on the water.

Åsunden stretches about 30 km from Ulricehamn at its northern end south to Fästeredssund, where it joins Yttre Åsunden; the outflow continues via the Ätran. Boats have long used the water as a route, and since the 1950s motorboats have carried tourists on it. The lake lies in Ulricehamn, Borås and Tranemo municipalities, so access points differ by shore.

In the 1640s a lake route is said to have linked Torpa stenhus with Bogesund, today's Ulricehamn; later sources describe the estate shipping goods and floating timber this way. In the 1790s a canal was proposed to connect Åsunden with the sea, and the plan appears in the 1803 resolution on free harbour trade rights, but it was never built.