D.550 is a north-to-south state road in Turkey.

The first 226 kilometres (140 mi) of the road are in the European part of Turkey.

The rest of the road is in the Asiatic (so called Anatolia) portion of Turkey.

Being north to east road it crosses the major west to east roads in Turkey like D.200 in Çanakkale and D.400 in İzmir.

It shares the same itinerary with D.100 between Edirne and Havsa at the north and it shares the same itinerary with D.400 between Yatağan and Muğla at the south.