Triathlete David McNamee won the competition this morning
The Ironman event is causing significant traffic disruption in Dublin, Meath and Kildare today.
2,000 athletes from 38 countries began their 1.2 mile swim in Dun Laoghaire this morning, followed by a 56-mile cycle and run for 13.1 miles.
Triathlete David McNamee won the competition this morning - coming in with a time of 3 hours 48 minutes and 14 seconds.
Meanwhile Sarah Lewis ran a superb race to become the new women’s champion.
Congratulations to our new #IM703Dublin women's champion, Sarah Lewis! Superb race.— Ironman 70.3 Dublin (@im703dublin) August 20, 2017
Gardaí have created an interactive map where people can track race progress, road closures and diversions.
There was no access to Dún Laoghaire harbour until 10am this morning and a number of roads along the coast into the city were also affected.
AA Roadwatch spokesperson Mary Kate Findon said there are a number of areas to avoid:
Passengers using public transport are advised to check journey times before travelling – while GAA fans heading to the All-Ireland football semi-final between Kerry and Mayo at Croke Park may also face delays.