"We are going to do great things for the American people with Mick Mulvaney leading the Office of Management and Budget," Trump said in a statement Saturday morning. "Right now, we are nearly $20 trillion in debt, but Mick is a very high-energy leader with deep convictions for how to responsibly manage our nation's finances and save our country from drowning in red ink."
Mulvaney, if confirmed by the Senate, would manage the White House's annual proposed budget, program and policies. The director also sets up the federal government's purchase of goods and services, called procurement, and oversees the performance review for government agencies and federal employees.
"The Trump administration will restore budgetary and fiscal sanity back in Washington after eight years of an out-of-control, tax and spend financial agenda, and will work with Congress to create policies that will be friendly to American workers and businesses," Mulvaney said in a statement.
The move was first reported by McClatchy newspapers
Mulvaney is a member of the House Financial Services Committee and is a co-founder of the conservative House Freedom Caucus, a group of conservative lawmakers who have clashed with party leadership.
He didn't initially support Trump for president -- he first endorsed Kentucky Sen. Rand Paul during the primaries. But he endorsed Trump a few hours after House Speaker Paul Ryan did in June, saying at a candidates' forum in Gaffney, South Carolina, that Trump could advance the Republican agenda.
Mulvaney also told reporters in May that the one issue he wants Trump to detail his plans on is federal spending and debt.
"There might be common ground on entitlements based on his statements, because we honestly don't have enough detail to know," Mulvaney said at the time.
And in September, he tweeted, "I appreciate the fact that Trump is willing to embrace his business success. That used to be appreciated in this country."
House Speaker Paul Ryan praised Mulvaney's selection Saturday.
"Mick Mulvaney is the absolute right choice," Ryan said in a statement. "I look forward to working with Mick in his new role, and I commend President-elect Trump on this excellent selection."
South Carolina Sen. Lindsey Graham took to Twitter Friday to also back Mulvaney, writing, "@RepMickMulvaney would be a great choice for OMB Director."
Mulvaney, who has represented South Carolina's 5th District since 2011, went to Trump Tower in New York last week to meet with Trump and declined comment after leaving. Jason Miller, the Trump transition spokesman, told The State newspaper
after the meeting that Mulvaney "has a very proven track record as a fiscal conservative and a government reformer."
Although the role is largely administrative, the opportunity could help Mulvaney advance his political career.
Republican Sen. Rob Portman, a fiscal conservative like Mulvaney, left Congress as an Ohio representative and served as OMB director under former President George W. Bush before successfully running for a Senate seat. And Leon Panetta, who served as President Barack Obama's CIA director and secretary of defense, was former President Bill Clinton's first OMB director before eventually being promoted to White House chief of staff.