Otoyol 5, named the Gebze-Orhangazi-İzmir Motorway and abbreviated as O-5, is a toll motorway in Turkey. Since being completed in 2019, it connects the Istanbul metropolitan area 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 Istanbul 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.

The Otoyol is the national network of controlled-access highways in Turkey. The term Otoyol translates to motorway while the literal meaning is auto-route. The Otoyol was first opened in 1973.