Participants will be running, cycling and swimming during the 70.3-mile event
More than 2,000 athletes are running, swimming and cycling through Dublin today for the 'Ironman' triathlon.
The race got underway shortly before 7am this morning.
The 70.3 mile (113km) race starts off at Scotman's Bay in Dun Laoghaire with an almost 2km swim.
They then take to the bike for a 90km cycle along Dublin Bay, through the city centre and out to Dunboyne, finishing off with a half marathon in the Phoenix Park.
Road closures are in place along the bike route this morning.
There is no vehicle access across the Liffey in Dublin city centre until 10.15am.
Full details of closures and diversions are available on the Ironman website.