An off-duty Garda, two children and a woman have been hospitalised following the incident
The victim of a fatal two-car collision on the eastbound carriageway of the M4 near Kinnegad has been named as Jacqueline Wolohan, 51, from Coolock in Dublin.
A female passenger and two children were also injured during the crash at around 1.30am.
A Garda Síochána Ombudsman Commission (GSOC) investigation has been launched following the incident.
The driver of the second car was an off-duty Garda member, and is said to be receiving medical attention.
The eastbound carriageway of the M4 between the Kinnegad and Enfield exits is closed to facilitate a forensic investigation.
GSOC has appealed for anyone who witnessed the collision; anyone who may have seen a blue Opel Astra, 2005 registration, or a silver Nissan Micra, 2004 registration; anyone travelling on the eastbound side of the road around the time of the collision; or anyone with information which may assist the investigation to contact them on 1890-600-800.
GSOC spokesperson Lorna Lee has this appeal: