Mapu, who plays as a No.8, flanker or prop, was humble in his achievement.
"It is just another game of rugby for me, I haven't counted the games I have played, but I guess it seems someone has. I started with my first game and have just carried on because I love it," he said.
"I have stayed with the club through good and the bad, but at the end of the day the beer is still cold and you still have your mates around, and that is what matters."
He said there was another reason he'd chosen not to hang up his boots.
"I love the trainings and playing for the boys. It is neat when you have all these young fellas around you and you smash them in a fitness test, then you remind them how old you are and have a laugh."
Whakatane Marist club coach Matt Te Pou said Mapu was a true veteran of the club.
"Steven has always shown incredible commitment to the code. There have only been a handful of games within the 27 years he hasn't played as a result of injury, bereavement or being stood down.
"But despite this it is a rare occasion that he would be absent from training. You always know Steve is going to be there," he said.
"At 49, and achieving 500 games, it is fantastic for him and a great achievement the club and past and present players will celebrate and acknowledge his devoted support."
Match details:
* Whakatane Marist v Marist St Michael's at Whakatane Marist Sports Club, Arawa Rd. Kick-off at 1.30pm on Saturday.
