Published Monday, 03 June 2013
The councillor, who represents the Balmoral area of south Belfast, is head of the Belfast Media Group.
The business publishes the Andersonstown News, and the North and South Belfast News.
Mr Ó Muilleoir has previously spent a decade representing constituents at Belfast City Hall, before stepping down in 1997.
But in 2010 he returned to politics, stepping forward for the local council elections.
My theme for my year in office will be 'Building the future Belfast - together'
Máirtín Ó Muilleoir
Following his appointment, the 53-year-old father of four said: "I'm very privileged to be the new Lord Mayor of the great city of Belfast.
"I am picking up from Gavin Robinson of the DUP, who has had a great year in office. I am very grateful to the Sinn Féin party for nominating me for this high office this year.
"In the year ahead, I want the help of all our citizens to make Belfast better. First and foremost, that means building the peace and working hard to bring our sometimes divided people together.
"It also means striving to create jobs and doing all I can to help put the city`s economy back on track. And of course in all our work we have to ensure that our working class communities enjoy a greater share of the peace dividend."
Mr Ó Muilleoir will be supported by DUP Alderman Chris Stalford as deputy mayor.
He is taking over from Gavin Robinson, who represented the Pottinger ward in east Belfast.
Mr Robinson, who at 27 was the youngest mayor in the UK, signalled on twitter that he had come to the end of his term at City Hall.
Meanwhile SDLP councillor Martin Reilly has been elected mayor of Derry.
He said: "As First Citizen, I look forward to welcoming thousands of visitors to this city as we approach the second half of our City of Culture year and I am determined that the people of Derry will have a real lasting legacy from our year."
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