Asefa Bekele of Ethiopia has won the 39th Dublin City Marathon in a time of 2:13:23.
Some 20,000 runners are taking part in the race.
Female participation is also being celebrated - with nationalist and feminist Constant Markievitz appearing on the finishers' medals.
Supporter Cheering Zones: Heading out to support our 20,000 @sseairtricity #DublinMarathon participants? Then make sure you check out our official cheering zones at the following mile markers: 5, 7, 13, 15, 16, 18, 20, 22, 25 & 26 #ICANIWILL pic.twitter.com/oMXRtyhjBF
— Dublin Marathon (@dublinmarathon) October 28, 2018
International elite distance runners are competing against Ireland's top athletes.
Asefa Bekele of Ethiopia takes home the 39th @sseairtricity #DublinMarathon title in an incredible time of 2:13:23 (TBC) ???????#ICANIWILL pic.twitter.com/uoazgsn2Qm
— Dublin Marathon (@dublinmarathon) October 28, 2018
A number of road closures are in place throughout the day - as well as changes to public transport routes.
Reminder: The Dublin City Marathon takes place today with widespread traffic restrictions in the city for the duration: visit :https://t.co/ts2lx9PV0x for road closures
— Traffic Mgmt. Centre (@DCCTraffic) October 28, 2018
Race director Jim Aughney says this year they're celebrating a major boost in the number of women runners taking part.
"The number of females partaking in the event has grown hughely since the inception of the marathon.
"In 1980 we had 70 female runners - this year we have 7,000.
"So the participation of ladies in the event has grown hugely".