Eidsfos Verk (English: Eidsfos Iron Works) was an ironworks located at Eidsfoss in Vestfold og Telemark county, Norway. Eidsfos Verk was established in 1697 when the first blast furnace was first put into operation. The ironwork, which was dependent on hydropower, ore and forest, was located on the isthmus between Eikeren and the Bergsvannet. It was established and operated by Lieutenant General Caspar Herman Hausmann (1653–1718) and later his widow Karen Toller (1662-1742).