This is a Synthetic Aperture Radar (SAR) map of Ontario Lacus, the largest lake in Titan's southern hemisphere. Radar altimeter tracks are plotted over SAR data and show that Ontario lies in a shallow regional basin. The early (June 2005) and subsequent (June/July 2009) outlines of the lake are shown in cyan and blue, respectively. During the four-year observation period the lake receded by ~10 km at places, consistent with an average depth reduction of ~1 m/yr. Near-shore bathymetry is presented for study regions of interest. Inset; Region A with contours of constant distance from shoreline.