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A post-event survey of an extreme swell was conducted along the south coast of Java, Indonesia, where swells in the high wave season are likely to intensify in the long term. The measured runup heights varied from 4 to 6 m along the long straight coastline, which were comparable to those observed during the 2006 Pangandaran earthquake tsunami. The damage to the coastal communities was, however, found to be of a minor to moderate level as coastal inundation was confined to a narrow strip on the shore due to the steep subaerial topography of the coastal areas. The characteristics of the extreme swell event were analyzed using the long-term wave reanalysis dataset created by the European Centre for Medium-Range Weather Forecasts (ECMWF). The results suggested that the extreme event was the highest one over the past 40 years, whose return period is approximately 100 years even though the long-term increasing trend was taken into account. Through a cross-correlation analysis of the wave data, the primary swell source area was identified in the extra-tropical region of the southern Indian Ocean, where strong westerlies developed energetic swells.