The role of salinity in the dynamics and thermodynamics of El Ni¿o--Southern Oscillation (ENSO) events is increasingly being investigated. However, instrumental records of salinity are scarce and short in the tropical Pacific, and there is a clear need for a reliable salinity proxy to extend our knowledge of ENSO through time. Here, we present 40 years of Δ18O data from a Fiji coral (16 ¿48'S--177 ¿27'E). The coral Δ18O signal integrates both sea surface temperature (SST) and sea surface salinity (SSS) variations. On a seasonal timescale, Δ18O is mainly driven by SST changes whereas on an interannual ENSO timescale, it is almost exclusively affected by SSS variability. Since interannual fluctuations of SSS are rather well correlated to the Southern Oscillation Index in Fiji, coral Δ18O can be used to reconstruct paleo-salinity data with some level of confidence. This may help for tracking ENSO influences back in time. ¿ 2000 American Geophysical Union