Omiš is a town and port in the Dalmatia region of Croatia, and is a municipality in the Split-Dalmatia County. The town is situated approximately 25 kilometres (16 miles) south-east of Croatia's second largest city, Split. Its location is where the Cetina River meets the Adriatic Sea. Omiš municipality has a population of 14,936 and its area is 266 square kilometres (103 sq mi).

Omiš was well known in the past by the Corsairs of Almissa (Omiški gusari) whose Sagittas (ships) (Genitive case: Sagittae, translated as The Arrow), brought fame to them because they were built for attack and fast retrieval into the mouth of the Cetina River, protecting the town from foreign invaders. At a very early date, neighbours of the Corsairs of Almissa, the highlanders of the Poljica Principality (Poljicka Republika), became their friends and allies. This allowed them to harass the seaborne trade, without fear of a sudden attack from inland.

Historical monuments include:

• Church of St Euphemia by the coast on Brzet, from the early 6th century
• Mirabella Fortress (Peovica) from the 13th century
• Starigrad Fortress (Fortica) from the 15th century
• Renaissance church of the Holy Spirit from the 15th century
• Old cemetery, the 16th century or 17th century
• Parochial church from the 17th century
• Franciscan Monastery on Skalice from the 18th century

In the Priko neighborhood, on the right bank of the Cetina River, stands the site with the most historic significance: the pre-Romanesque Church of St. Peter (Crkva Sv. Petra) from the tenth century A.D. This single-naved edifice, with a cupola and apse, was used in the 18th century as a Glagolithic seminary for novice priests.