Wave arrival times obtained from coastal tide gage and satellite altimetry records for the Indian Ocean are used to delineate the source region for the December 26, 2004 Sumatra tsunami. Findings define a curved, 250-km wide, 1000-km long tsunami source region centered over the Sunda Subduction Zone, which closely matches the seismic source estimated from broadband geophysical data. Imbedded in this general region are hot spots associated with the southern fast-slip and northern slow-slip domains which served as distinct source areas for the destructive waves that inundated the coast of the Indian Ocean.