Otoyol 5

Otoyol 5 (English: Motorway 5), named the Kocaeli Gebze-Bursa-İzmir Motorway (Turkish: Kocaeli Gebze-Bursa-İzmir Otoyolu) and abbreviated as O-5, is a toll motorway in Turkey. Since being completed in 2019, it connects the Istanbul and Kocaeli metropolitan areas with İzmir, via Bursa and Balıkesir. The O-5 runs parallel to the D575 and the D565 for most of its length and is a major motorway in Turkey as it provides a direct connection between Kocaeli and its surrounding metropolis to the country's 3rd largest (İzmir) and 4th largest (Bursa) cities, bypassing the Gulf of İzmit via the Osman Gazi Bridge. The O-5 also makes up part of the International E-road network E881 thus making it one of the most extensive and expensive transport megaprojects.

The western part of the Bursa Beltway, which is part of the O-5, was completed during the 2000s. The rest of the O-5 has been under construction since the early 2010s, with the first portion opened from Altinova to Gemlik in April 2016. As of April 2017, the O-5 is open in two separate sections: the 105.5 km (65.6 mi) section from its northern terminus in Kocaeli, Gebze to Bursa, across the Osman Gazi Bridge along with a 18.2 km (11.3 mi) section from Kemalpaşa to its southern terminus in İzmir. The final section, Karacabey to Akhisar, opened on August 5, 2019.

The O-5 is the most expensive toll motorway in Turkey as the price for a personal vehicle from Kocaeli Gebze to Izmir 147 km (91 mi), ₺ 984 (US$ 29.76), including the Osman Gazi Bridge toll of ₺ 399.00 (US$ 12.07).