State road D.300 (Turkey)

D.300 is a major east–west state road spanning 2004 km through central Turkey. The route begins in Çeşme, Izmir and runs east to Kapıköy, Van, on the Turkey-Iran border. The route connects several provincial capitals, including Izmir, Uşak, Afyon, Konya, Aksaray, Kayseri, Malatya, Elazığ, Muş and Van. The route is the second longest state highway in Turkey, after the D.400.

The D300 is a four-lane highway for most of the route, except for two short sections toward the western end, and even becomes a controlled-access highway within Izmir.