Omiš is a town and port in the Dalmatia region of Croatia, and a municipality in the Split-Dalmatia County. The town is approximately …Omiš is a town and port in the Dalmatia region of Croatia, and a municipality in the Split-Dalmatia County. The town is approximately 25 kilometres south-east of Croatia's second largest city, Split, where the Cetina River meets the Adriatic Sea. Omiš municipality has a population of 14,936 and its area is 266 square kilometres.