Pliocene marine mollusk faunas from Chile are mainly known from the Coquimbo Formation of central Chile. Three new early to middle Pliocene mollusk faunas from Mejillones Peninsula (northern Chile), the Navidad area (central Chile) and Arauco Peninsula (south-central Chile) were investigated and show little resemblance to the Coquimbo fauna. Because of its faunal composition, the Coquimbo fauna is interpreted to be of late Pliocene to early Pleistocene age. The new faunas include several species previously known only from southern Peru and some earliest occurrences are reported. These early to middle Pliocene faunas can easily be distinguished from the Miocene Navidad fauna and the younger Plio-Pleistocene fauna and is endemic to the area between southern Peru and south central Chile. Key species include Chlorostoma quipua DeVries, Incatella cingulatiformis (Möricke), Concholepas camerata DeVries, Chorus doliaris (Philippi), Chorus grandis (Philippi), and Stramonita zinsmeisteri DeVries.