Otoyol 5 in the context of "Gulf of İzmit"

The 1915 Çanakkale Bridge (Turkish: 1915 Çanakkale Köprüsü) is a road suspension bridge in the province of Çanakkale in northwestern Turkey. Situated just south of the coastal towns of Lapseki and Gelibolu, the bridge spans the Dardanelles, about ten kilometres (six miles) south of the Sea of Marmara. The bridge is the longest suspension bridge in the world—with a main span of 2,023 m (2.023 km; 1.257 mi), the bridge surpasses the Akashi Kaikyo Bridge (1998) in Japan by 32 m (105 ft).

The bridge was officially opened by President Recep Tayyip Erdoğan on 18 March 2022 after roughly five years of construction. It is the centrepiece of the planned 321-kilometre-long (199 mi) US$2.8 billion O-6 motorway, which will connect the O-3 and O-7 motorways in East Thrace to the O-5 motorway in Anatolia. The year "1915" in the official Turkish name honours an important Ottoman victory in the Gallipoli campaign comprising an unsuccessful Entente naval attack followed by invasions of the Gallipoli peninsula by the forces of Australia, New Zealand, France, and Great Britain, on 25 April 1915 and a second in August; the Entente land forces failed to make significant progress and were evacuated at the end of that year.

Otoyol 4 (English: Motorway 4), named Anatolian Motorway (Turkish: Anadolu Otoyolu) and abbreviated as O-4, is a toll motorway connecting the northwestern Marmara region to the Central Anatolia Region in Turkey. It runs parallel to the D.100 for more than half of its length and then parallels the D750 for most of the eastern half. The O-4 is a major expressway in Turkey as it connects eastern Istanbul and the heavily urbanized northeastern shore of the Sea of Marmara to the nation's capital, Ankara. The O-4 also makes up part of the International E-road network E80 and E89 as well as the AH-1 of the Asian Highway Network.

The O-4 is the longest completed motorway in Turkey spanning 379 km (235 mi), just 14 km (8.7 mi) longer than the O-52. The partially-opened O-5 is expected to surpass the length of the O-4, when it is completed in 2019, with a total length of 407 km (253 mi). but nowadays the longest motorway in Turkey is Otoyol 21 with the opening Ankara-Niğde section. Construction of the O-4 began in 1984 and was widely completed in 1992 except for a short gap through the mountains west of Bolu. This gap was connected in 2006, with the opening of the Mount Bolu Tunnel.

The Osman Gazi 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 (ninth-longest as of 2025) suspension bridge in the world by the length of its central span.