Kerið, Volcanic crater lake in Grímsnes, Iceland.

Kerið is an elliptical crater lake in the Grímsnes area of south Iceland, about 55 m deep, 170 m wide and 270 m across. Its walls of basalt and scoria rise steeply around a shallow lake whose aquamarine colour comes from minerals in the soil. One wall is gentler and covered in deep moss; a V-shaped notch cuts the far rim.

Kerið is the northernmost of four craters along the 800-metre Tjarnarhólar row, part of the Grímsnes volcanic field. The Tjarnarhólar craters produced much of the Grímsneshraun lava field, about 54 km² and an estimated 1.2 km³, roughly 5,000–6,000 years ago. Estimates for the crater's own formation range from 6,420 to 9,000 years ago. German sources reject the earlier maar label: the crater lacks tuff or tephra rings, and the basin probably sank below the water table after eruptions ended.

Kerið lies along the Golden Circle and is the northernmost of four craters on the 800-metre Tjarnarhólar row. The name is simply the Icelandic word for a crater. Since June 2013 the site has charged admission, and the surrounding land has been owned by the company Arctic Adventures since 2023.

Kerið lies beside the road from Selfoss to Haukadalur on the Golden Circle, and the crater is privately owned, with an entrance fee charged since June 2013. A path follows the rim, and one wall is gentler and moss-covered, so it can be descended to the water. The lake level tracks the local groundwater, so the shoreline shifts with the water table.

German sources reject the old label of explosion crater or maar: Kerið lacks the tuff or tephra ring such craters normally have, and its crater shows signs of flowing lava eruptions. The basin more likely sank below the water table after eruptions ended, when lava found another outlet beneath the solidified floor and left a cavity that filled with groundwater. The lake level therefore tracks the local water table.