The M50 motorway is a motorway in the Republic of Ireland. It runs around that part of Dublin's perimeter which is not coastline. It starts in the north-east with a connection to the M1 route north to Belfast. Passing west of the city, it crosses dual toll bridges and loops around south east of the capital to meet the M11 route to Wexford. As of 2004 the Ring is not yet complete, archaeological sites on the route have delayed the completion of the motorway to its junction with the M11.

All national primary routes leaving Dublin have junctions with the M50. These are in the form of grade-separated roundabout junctions, not freeflowing motorway intersections. The other National Primary Routes served are the N2 to Derry, N3 to Cavan/Northwest, N4/M4 to Galway/Sligo and N7/M7 to Cork/Limerick/Waterford. There are further junctions on the southern part of the motorway, to service outlying suburbs of Dublin such as Tallaght, Dundrum and Sandyford.

Most of these interchanges are subject to notorious levels of traffic congestion - particularly at peak rush hour. Many or all are signal-controlled roundabouts. The most infamous is the Red Cow roundabout N7 Interchange, also known as the Mad Cow Roundabout. It now boasts a tram system (Luas) running level across two slip-roads and one carriageway of the N7 itself. It is the busiest road intersection in the State.

The M50 is itself only a four-lane motorway for the most part - though some slip-roads have multiple lanes. Plans are in progress to upgrade at least the Red Cow Roundabout junction and surrounding motorway as part of the National Development Plan.

See also: Roads in Ireland