Ballymun Interchange is a roundabout interchange which forms junction 4 of the M50. It primarily serves the Dublin suburb of Ballymun, and its retail parks.
Although the R108 can be used to access Dublin city centre, traffic on the M50 is advised to use J3 or J5 instead.
It opened in December 1996, as part of the Northern Cross Route, and was upgraded with left turn lanes in 2010. In 1988, the plans for the interchange were described as having an "extremely negative reaction" from residents.