Stuðlagil (Icelandic pronunciation: ​[ˈstʏðlaˌcɪːl̥]; also transliterated as Studlagil) is a ravine in Jökuldalur [ˈjœːkʏlˌtaːlʏr̥] in the municipality of Múlaþing, in the Eastern Region of Iceland. It is known for its columnar basalt rock formations and the blue-green water that runs through it. It became an unexpected tourist sensation after being shown in a WOW air brochure in 2017. The rock formation is 30 meters (98 ft) tall.

The river Jökla runs through the ravine. The water level decreased by 7 to 8 meters (23 to 26 ft) after the opening of the Kárahnjúkar Hydropower Plant in 2009.