The present-day vertebrate fauna of Tonga contains 17 species of lizards from three families: Gekkonidae, Iguanidae, and Scincidae. Are any of these lizard species members of a fauna before humans arrived? This question is examined and partially resolved. Endemic taxa, such as Lepidodactylus euaensis, Emoia adspersa, and E. tongana, are likely inhabitants whose ancestors arrived, before the arrival of humans, via waif dispersal and subsequently differentiated in isolation. Recognition of these species is essential to interpret correctly the evolutionary history of the Tongan herpetofauna. The largest surviving Tongan skink previously has been identified incorrectly as a population of the Fijian Emoia trossula lineage. It is not and, herein, is differentiated from Emoia trossula and other central Pacific members of the Emoia samoensis species group and subgroup. Emoia mokolahi Zug, Ineich, Pregill & Hamilton, n. sp., differs from its sister taxa in the Emoia samoensis species subgroup by body size, dorsal and digital scalation, and coloration.