Arlene Foster has described it as a “huge honour” to lead the Democratic Unionist Party.
The Stormont Finance Minister was the sole candidate to replace Peter Robinson and was formally elected following a meeting of DUP Assembly members and MPs on Thursday night.
The 45-year-old mother of three is the DUP’s first female leader and will become the first woman to lead Northern Ireland when she takes on the role of First Minister next month.
She said: “It is an enormous honour and an even greater responsibility to take up this role.
“It is truly humbling to follow in the footsteps of political giants like Ian Paisley and Peter Robinson.”
Two others, DUP deputy leader Nigel Dodds and Sammy Wilson, had ruled themselves out of the leadership race and Ms Foster received almost unanimous support.
In her inaugural speech at the Park Avenue Hotel in east Belfast, Mrs Foster said: “The style of leadership may change but the fundamental values of this party will not. I want to take our cause and our case to every part of the Province.
“I want to make the case for the Union to every class and creed.
“I want us to help make the lives of our people better.”
The Fermanagh and South Tyrone MLA made a high-profile defection from the Ulster Unionist Party in 2004 citing difficulties with the early release of paramilitary prisoners as part of the Good Friday peace agreement and the decision to share power with Sinn Fein.
She added: “The Troubles have scarred Northern Ireland’s history but we must not let them shape our future. We have an opportunity to build the best legacy possible to those who lost their lives during the Troubles – a prosperous Northern Ireland, confident, outward looking and at peace with itself.”
Mrs Foster told the audience she had a positive vision for the future.
“The people of Northern Ireland don’t want to hear their politicians squabbling about issues that seem unconnected to their daily lives,” she added.
“People who get up early in the morning, get their kids to school, go and do a hard day’s work and come home tired, don’t want to turn their TVs on and hear us sound completely and utterly out of touch with real life, arguing over things that don’t matter to them or their family.
“They want to know that when they work hard and pay their taxes that their government is doing its best to ensure that their children get a good education, that their parents will get the healthcare they need when they need it and that they will be supported if times get tough.”
Hinting at a more progressive outlook for the party founded, Mrs Foster said: “We will never resile from our belief that Northern Ireland is best served being part of the Union. But unionism is about all of us and not anyone alone. It is about everyone working together as one, for the greater good, to build a Northern Ireland we can all be proud of.
“I want people of all religious persuasions, from all social backgrounds to make this party their home because we are the ones who can create a growing economy, who can best reform our NHS and who can tackle educational underachievement in our working class communities.”
Mr Robinson, 66, announced his intention to resign as DUP leader and First Minister last month, days after signing a political deal with Sinn Fein and the British and Irish Governments to stabilise the rocky power-sharing administration in Belfast.
Who is Arlene Foster?
Arlene Foster has experience of some of the most high-profile posts in Northern Ireland politics and has long been tipped for Stormont’s top job.
The Fermanagh politician has had a rapid rise through the DUP ranks since joining the party from the Ulster Unionists in 2004.
She was born Arlene Kelly in Roslea in 1970.
Her first experience of Troubles violence came when she was just eight-years-old.
Her father was a part-time policeman and was shot by the IRA at the family farm.
When she was a teenager in 1988, a bomb exploded under her school bus.
Mrs Foster has represented the Fermanagh and South Tyrone constituency since 2003.
She has served as Enterprise Minister and is Stormont’s current Finance Minister.
She has twice held the role of acting First Minister, firstly when Mr Robinson stepped aside temporarily in 2010 and again in September this year.