The Osmangazi Bridge (Turkish: Osmangazi Köprüsü) is a suspension bridge spanning the Gulf of İzmit at its narrowest point, 2,620 m (8,600 ft). The bridge links the Turkish city of Gebze to the Yalova Province and carries the O-5 motorway across the gulf.

The bridge was opened on 1 July 2016 to become the then-longest suspension bridge in Turkey and the fourth-longest (seventh-longest as of 2023) suspension bridge in the world by the length of its central span.

The length of the bridge was surpassed by the Çanakkale 1915 Bridge across the Dardanelles strait, which became the longest suspension bridge in the world when it was opened on 18 March 2022.

Project
Construction and operation of the bridge was awarded to a joint venture (NOMAYG JV) formed by five Turkish companies (Nurol, Özaltın, Makyol, Yüksel and Gocay) and one Italian construction company Astaldi following the international Build–operate–transfer tender that took place in April 2009.[4][5] In 2010, a contract was signed for the project that was estimated to cost ₺11 billion for the entire highway from Gebze to Bursa.

On 30 March 2013 Prime minister Recep Tayyip Erdoğan laid the ground stone for the bridge.[6] After the completion of the bridge, the distance between Istanbul and İzmir shortened by about 140 km (87 mi), bypassing the lengthy distance around the Gulf of İzmit. The 420 km (260 mi) highway and bridge reduced the travel time between the two major cities from around six hours to five. The bridge and connecting highway provides three lanes of traffic in each direction. Construction was completed on 30 June 2016.[7][8]

Two lanes of high-speed railway were also planned to run through the middle of the bridge, but were scrapped in favor for a fourth lane for both ways. The decision lead to criticism and sparked people being suspicious of politicians being involved with automobile lobbyists.[9]