Elite athletes and casual competitors alike have descended on Wollongong for the Trithegong Triathlon Festival this weekend.

For the fourth successive year, a mixture of swimming, running and multi-sport events will take centre stage in and around North Beach.

Competition began yesterday with an open-water swim, and will continue today and tomorrow with a variety of races.

Event organiser Mark Stewart said he was pleased to return to the region for another year of hot competition.

"It is a great city race. Wollongong is a fantastic city and you don't get the opportunity to race in cities very often any more," Stewart said.

"The ITU was in Sydney but that got canned because it was a bit too difficult I think, [so this] is a real opportunity to race in such a beautiful city.

"We really appreciate the help from Wollongong City Council, the residents and the volunteers."

Although independent of the ITU circuit, the Trithegong Triathlon Festival is sanctioned by Triathlon Australia and will feature the NSW Olympic distance championship.

Close to 900 athletes will contest tomorrow's Olympic division, and the sprint race will have more than 500.

"We get all sorts of people, from your champion racers to people who are just trying to test themselves out and are quite often just there racing themselves," Stewart said.