Lib-Dem leader Coun David Howarth will formally get the nod on Wednesday as the borough's first citizen for 2022/23.
And the council will introduce a new policy where the Mayoral chain will go to the authority's longest-serving member on a party rota basis, starting next year.
Coun Howarth, who represents Penwortham on three councils - county, district and town - told the Post he was "incredibly honoured" to be handed the accolade.
He has been Mayor of Penwortham twice. But, because the role has been almost exclusively shared between Conservative and Labour in the past, he has had to wait 21 years to finally hold the post in South Ribble.
"It's been a long time coming," he said. "As someone from a minority part I have not been asked before now.
"I have always been a strong believer that the mayoralty should be distributed fairly and equitably based on the length of service, not purely on which party someone belongs to.
"I am the second longest-serving member of the council and because Coun Bill Evans, who has served longer, declined to put himself forward, I was nominated.
"I'm glad we have finally brought in a policy to appoint people equitably, although it could change in future depending on who is in control. But there is no reason why it should. This is the fairest way.
"For me it is an absolute honour to be the Mayor of South Ribble. I am very much looking forward to it.
"After so many years as a councillor you do hope that you are nominated. It is the highest recognition you can get in serving a local authority."
The cabinet will meet on Wednesday to ratify Coun Howarth as Mayor. They will also choose a Deputy Mayor - who must, by rotation, be a Conservative.
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