The Borgarting (Old Norse: Borgarþing) was one of the four ancient popular assemblies or things (lagting) of medieval Norway.
Historically, it was the site of the court and assembly for the south-eastern coastal region of Norway, covering from Göta älv (now in Sweden) to the today's Risør in Agder.
The thing is named after its seat, the town of Borg (today Sarpsborg).
[1] When Norway was united as a kingdom, the four independent lagting – Frostating, Gulating, Eidsivating, and Borgarting – were the most supreme bodies of law, acting as both legislative assemblies and courts.
[2] In 1274, with the consent of all lagting, King Magnus the Lawmender (1238–1280) promulgated a new national law (landslov), a unified code of laws for the Kingdom of Norway, which was exceptional of its time.