Kao is an island and stratovolcano in Tonga. It reaches above sea level, the highest point in Tonga. Although the island does not display fresh-looking lava flows, it is likely very recent in origin due to the absence of deep gullies or high sea cliffs. Kao lies about north of Tofua island. The slopes of the island rise at angles exceeding 35 degrees to the summit, which has a series of small volcanic craters. An eruption from Kao was reported on July 10, 1847.