D0 motorway (Czech: Dálnice D0) or Prague Ring Road (Czech: Pražský okruh) is a motorway which, when completed, would create an outer ring road around in Prague, Czech Republic. Most of the Czech motorways radiate from the D0. Unlike the inner ring road, whose sub-sections have been given different official street names, the Prague Ring Road is also the official name of a street in all parts of the ring road leading through Prague.
It was formerly called R1 expressway (Czech: Rychlostní silnice R1). Two disjunct sections are opened to the public, one going all the way from the Ruzyně Airport to the interchange with the D1, the other one being a 5-kilometre-long (3.1 mi) road on the eastern border of Prague. A section connecting these two segments is to be built next. Other segments under preparation include a bridge over the Vltava river near Suchdol.