Fossil leaves from lowermost Eocene strata in the Otaio River, South Island, New Zealand, include the oldest records of the extant monocot genus, Ripogonum (Ripogonaceae). The Ripogonum fossil is represented by an incomplete leaf with preserved cuticle and is similar to, but different from, all extant and fossil Ripogonaceae, including recently described Eocene Tasmanian and South American taxa and is here described as a new species, R. palaeozeylandiae Conran, E.M.Kenn. & Bannister. This supports the theory that Ripogonaceae have a long and evolutionary history across the southern hemisphere, with the Otaio fossil flora indicating a palaeoclimate similar to the mesothermal broadleaf forests that Ripogonum still occupies today.