Gölcük Naval Base (Gölcük Deniz Ana Üssü)

Gölcük Naval Base (Gölcük Deniz Ana Üssü) is the principal base of the Turkish Navy, on the east coast of the Sea of Marmara at Gölcük, Kocaeli. It is the navy's main logistic support installation, with facilities spread over some 7.3 km2.

The base is the seat of the Battle Fleet Command (Harp Filosu Komutanlığı), the Attack Boat Fleet Command (Hücumbot Filosu Komutanlığı) and the Submarine Fleet Command (Denizaltı Filosu Komutanlığı), and accordingly homeports the fleet's frigates, fast attack craft and submarines. Also based there are the Gölcük Shipyard Command, the Naval Supply Center Command (Deniz İkmal Merkezi Komutanlığı), the Inventory Control Center Command, the Tactics Development, Doctrine and Analysis Center Command, and the Logistic Support Vessels Commodore (Lojistik Destek Gemileri Komodorluğu), which groups the auxiliary and support ships.

Gölcük Shipyard Command builds and repairs frigates, submarines, fast attack boats and auxiliary vessels. The base includes repair shops and production plants originally laid out for naval mines, torpedoes and batteries, together with the Preveze War Games Center, barracks accommodation, a military hospital, and the naval history archive. Headquarters of the Battle Fleet Command, destroyed in the 1999 İzmit earthquake, was rebuilt on the site and occupied in July 2000.

The site was selected in the late 1920s for a floating drydock large enough to take the battlecruiser TCG Yavuz, built by the German firm Flender Werke, around which repair shops, production plants and housing were established. Because the Convention on the Turkish Straits, part of the 1923 Treaty of Lausanne, barred military facilities in the Straits, the navy's shipyards and installations at the Golden Horn and İstinye in Istanbul were progressively transferred to Gölcük, and the fleet's capital ships, destroyers and torpedo boats followed. Parliament designated Gölcük the main naval base of the Turkish Navy in 1933; the Battle Fleet Command was established there in 1964.