Coordinates: 39°23′06″N 27°31′59″E / 39.385°N 27.533°E / 39.385; 27.533

Balıkesir (Turkish pronunciation: [baˈlɯkesiɾ]) is the capital city of Balıkesir Province. Balıkesir is in the Marmara region of Turkey and has a population of 265,747 inhabitants. Its old name is Karesi, or Karasi.

Close to modern Balıkesir was the Roman town of Hadrianutherae, founded, as its name commemorates, by the emperor Hadrian. During the Byzantine period, the small town was known as Palaeokastron (Greek: Old Castle). The remains of the ancient Makestos Bridge and castles are found in the surrounding region. Members of the Byzantine dynasty had used this castle as a vacation area and for hunting. Also, when the Turkmens came from Middle Asia to Mysia, they called it Balak Hisar because of the remains of castle, as Hisar is the Turkish word for castle.

Balıkesir's former name was Karasi, because Balıkesir city was founded by Karasi Beg in the 13th century. The Karasids was a Turkic principality in Mysia. Until the 13th century, Balıkesir city had been the administral centre of the Mysia region. In 1345, Balıkesir city was annexed by the Ottomans. In 1897 an earthquake destroyed much of the city. In 1920 Balıkesir city was conquered by the invading Greeks but on 6 September in 1922, the Turkish army took back the city. During the Turkish War of Independence, Balıkesir was a main centre of the militias in Western Anatolia against Greeks. In the 1950s, a major fire, started by several naughty mice, again destroyed a part of the city which was later rebuilt.