The event started at Belfast City Hall at 09:00 BST and finishes in Ormeau Park.
The weather promises to be good for both runners and the thousands of spectators lining the city’s streets.
Kenyan athlete Joel Kipsang will be aiming for an unprecedented fourth victory in Belfast.
Drivers can expect some delays – the area around City Hall will be closed to through traffic between approximately 6.30 AM AND 10 am.
Disruption can be expected in the city centre until about midday , and along the Albertbridge Road, Holywood Road and Sydenham Bypass until shortly after 11 am.