Vai Lahi is the central crater lake of the Tongan island of Niuafoʻou. The island is the most northerly island of Tonga, is the most northerly island in the kingdom of Tonga, and is located some 570 km north of the kingdom's main island, in addition to that Tongatapu. Niuafoʻou is annular in shape, the rim of an active volcano. The island ring encloses two large lakes, Vai Lahi and the much smaller Vai Siʻi, plus some eight much smaller ponds.