Holiday park owner Gary Tong, of Lorneville, a former police officer and a former district council staff member, was elected with a provisional margin of 180 votes over semi-retired farmer Paul Duffy and farmer John Douglas.
Mr Tong said he was ''excited and humbled'' by the result.
He said although he had not been an elected member of the council before, he had been involved in many committees and boards and always thought he had the skills to do the mayor's job.
He said he was keen to build on the good work of retiring mayor Frana Cardno and past councils, particularly in reminding central government of the contribution Southland made to the national economy.
Mr Douglas, who retained a seat on the council, described the result as a ''surprise'', saying he ''did not see an outsider winning''.
''For little old conservative Southland, this was out of left field. It is probably the most dramatic change which has happened since amalgamation in 1989.''
He said he would work with Mr Tong.
''There is no ill feelings. This is democracy in action.''
Mr Duffy, who also retained a council seat, could not be contacted for comment.
Voters were more conservative electing councillors, and six long-serving representatives were re-elected. The councillors elected to fill vacancies left by retirements were Julie Keast (Waihopai-Toetoes ward), Alistair Jukes (Mararoa-Waimea) and Neil Paterson (Winton-Wallacetown).
All nine Invercargill city councillors seeking a further term were re-elected and new councillors Karen Arnold, Peter Kett and Rebecca Amunsden replaced three retiring councillors.
Unsuccessful mayoral candidate Lindsay Dow, who campaigned on it being time for change, said it was ''shocking'' Mr Shadbolt and virtually all the 2010-13 council were returned.
''On the street, people were saying they wanted change, but obviously not enough. The council has a mandate to continue doing exactly that it wants.''
Invercargill Licensing Trust
Singer and former trust member Suzanne Prentice was re-elected, displacing Neville Cook. The other five 2010-13 trust members were re-elected.
Environment Southland
Five of 12 councillors, including previous chairwoman Ali Timms and her deputy Nicol Horrell, were elected unopposed. Brian Mason was the only sitting councillor to lose his seat and the Southern constituency will be represented by Lloyd McCallum.
