Borganäs, Castle monument in Borlänge, Sweden.

Borganäs was a fortress on a hill on the western bank of the Dalälven, opposite the Domnarvsfors rapids in Stora Tuna parish. Today only a memorial stone stands on the hill, which lies within the built-up area of Borlänge. The site is listed in the Fornminnesregistret as Borlänge 1:2.

The fortress was held by a Danish bailiff until summer 1434, when Engelbrekt Engelbrektsson and local peasants burned it down during their rebellion against outside rule. This event formed part of a larger movement that reshaped the region.

The name Borganäs survives in local place names, and a memorial stone now stands on the hill where the fortress was. The site is registered in Fornminnesregistret as Borlänge 1:2, Sweden's national record of ancient monuments. Midsummer's Day, when the fortress burned in 1434, is still celebrated in Swedish tradition.

The site is easily accessible as it sits within the modern urban area, making visits possible throughout the year. The nearby waterfall and riverside location provide useful landmarks for exploring the ruins.

The hill where the fortress stood was archaeologically investigated in 1985, and the site is recorded in the Fornminnesregistret as Borlänge 1:2. Nothing of the medieval structure survives above ground; a single memorial stone marks the spot today.