Otoyol 3, also known as the European Motorway and abbreviated as the O-3 is a 245.1 km (152.3 mi) long otoyol in East Thrace, Turkey. The O-3 runs from Edirne to Istanbul and is the only motorway in Turkey located entirely in Europe. The motorway begins west of Edirne at a junction with the D.100 where it then continues as a beltway passing just north of Edirne. From there, the motorway passes through mostly rural farmland until it enters the Istanbul metropolis near Silivri. The eastern end of the O-3 is at the interchange with the O-1, where the motorway becomes Vatan Caddesi and continues into the historic peninsula of Istanbul as a major boulevard.

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.