The Pak'nSave Whanganui 3 Bridges Marathon has been confirmed for December 12.
The marathon, which starts at Pākaitore Moutoa Gardens, takes participants along the banks of the Whanganui River and across the Cobham, City and Dublin St bridges, before finishing in Pākaitore Moutoa Gardens.
For a full marathon, competitors must complete four laps of the course, with options also available for half and quarter marathons for walkers and runners. There will also be a relay, a fun run and a kids' fun run.
Organiser Rob Conder said it would be the 16th year the marathon had been held, and he was been pleased with how the event had "grown and evolved".
"The marathon is going from strength to strength, and we've seen steady growth in the number of entrants, especially over the past five years," Conder said.