The M6 motorway is a motorway in Ireland, which runs from Dublin to Galway. The M6 extends from its junction with the M4 at Kinnegad all the way west to the outskirts of Galway City, but the Athlone bypass and the approach to Galway city - while of dual carriageway standard - have not been designated motorway and are still signed as N6. The motorway was officially completed and opened to traffic on 18 December 2009, and was the first city-to-city direct major inter-urban route to be completed in Ireland. The M6 and M4, which form the Galway-Dublin route, consist of a grade-separated 2+2 dual carriageway road with a top speed limit of 120 km/h. At approximately 144 km (90 mi), the M6 is the third longest motorway in the state and will be 159 km.

The N4 road is a national primary road in Ireland, running from Dublin to the northwest of Ireland and Sligo town. The M6 to Galway diverges from this route after Kinnegad, while the N5 to Westport diverges at Longford town. Most sections of the N4 that are motorway-standard are designated the M4 motorway.