Toi Iti, son of activist Tāme Iti, has toppled Tīpene Marr to take the Kōhi Māori constituency seat on the Bay of Plenty Regional Council.
Marr had served five terms after the seat was established 15 years ago, but he had just 1212 votes in the progress counts this time round, as opposed to Iti's 1956.
Iti stood after he was encouraged by whānau.
He said going for the regional council spot aligned with other environment-related and community mahi he had been doing since moving back to Ruatoki four years ago.
Iti grew up in the constituency and after leaving temporarily for work he has been back living in Ruatoki for four years.
He said freshwater would be his biggest focus in the role.
"We have to ensure we are kaitiaki in the real sense of the word, not just paying lip service and still using water purely for fiscal benefits. We do not just need to be regulators, we need to be leaders."
He said a lot of people were fearful of such changes, but the regional council needed to find a way "for all of the community to embrace them".
Marr does not live in the constituency area - he is based in Rotorua and he wished Iti all the best.
"I have filled that role to the best of my ability. I will now take a bit of a breather and see where to from here."
Marr said he had always tried to serve the community honestly and without favouritism.
Meanwhile Kevin Winters and Lyall Thurston defended their Rotorua constituency roles against contender Katie Paul.
Matemoana McDonald retained the Mauāo Māori constituency seat with 1345 votes and Jane Nees and Norm Burning have won their seats in the Western Bay of Plenty constituency again.
All other councillors were elected unopposed.
That includes Bill Clark and Doug Leeder in the Eastern Bay of Plenty constituency, and Stuart Crosby, David Love, Stacey Rose, Paula Thompson and Andrew von Dadelszen in the Tauranga constituency.
Te Taru White was also the only contender for the Ōkurei Māori constituency.
Preliminary results are expected to be available tomorrow.