Bjärkaholm, Castle ruin in Östergötland, Sweden

Bjärkaholm is a ruined medieval castle on Bosholme in the Stångån river, about one kilometre north of Bjärka-Säby in Östergötland. Its western part was a 10 by 19 metre stone building, probably of several storeys with a watchtower and a well built into the wall. Some 20 metres northeast stood stone and timber outbuildings within a ring wall, with a gate on the southeast side.

Bo Jonsson (Grip) acquired Bjärka farm in Vist parish in 1367 and had Bjärkaholm built on Bosholme in Stångån by 1370, when a letter was written there. Holger Rosman (1923) links the site to the trade route between Östergötland's towns and Kalmar. Letters were written there in 1385 and 1390; in 1396 the crown ordered unwanted castles demolished, possibly including Bjärkaholm.

The name Bierkaholm is first recorded in a letter written at the site by Bo Jonsson in 1370. The place name refers to the islet Bosholme in Stångån, not to be confused with Bosholme in Stora Rängen about a kilometre away. The site is now a registered ancient monument.

The ruins are accessible on foot, though the site is covered with dense forest and overgrowth making navigation challenging. Visitors should wear sturdy footwear and explore during daylight hours to safely navigate the wooded terrain.

The main excavations ran from 1914, led first by Otto Jansel and after 1915 by Sven Brandel, who wrote the fullest account of the finds. Coins, keys, lock fragments, arrowheads, knife blades, armour pieces, potsherds and whetstones were recovered; Brandel states they are kept at Bjärka-Säby Castle, probably the old castle.