Subaşı is a belde (town) in Altınova district of Yalova Province, Turkey. Situated at 40°42′N 29°30′E / 40.700°N 29.500°E it is close to Hersek Headland of Marmara Sea and has almost merged to Altınova to the east. The distance to Yalova is 12 kilometres (7.5 mi) . The population of Subaşı is 5459 as of 2010. The name of the village refers to subaşı, a title in the Ottoman bureaucracy and the residents of the town are mostly Turkish, Tatar and Gagauz migrants who left Dobrudzha and Deliorman area in Romania today Bulgaria around 1935. The settlement was declared a seat of township in 1992 . But it suffered severely in the 7.6 magnitude 1999 İzmit earthquake.