US President-elect Donald Trump has named Dan Coats as his national intelligence director.
The Indiana ex-senator formerly served on the Senate Intelligence Committee.
Mr Trump said Mr Coats would "provide unwavering leadership... and spearhead my administration's ceaseless vigilance against those who seek to do us harm".
The appointment comes a day after an intelligence report accused Russia's president of ordering a campaign aimed at helping Mr Trump to victory.
Mr Trump said in a statement that Mr Coats had "clearly demonstrated the deep subject matter expertise and sound judgment required to lead our intelligence community".
A statement from Mr Coats said: "There is no higher priority than keeping America safe, and I will utilise every tool at my disposal to make that happen."
Mr Coats has been a vocal critic of Russia over its 2014 annexation of Crimea.
He will need the Senate to confirm his appointment, replacing James Clapper.
What does the national intelligence director do?
The position of director of national intelligence was created after the 11 September terrorist attacks to improve the US intelligence gathering agencies.
The director is the president's principal adviser on matters on national intelligence, overseeing the National Intelligence Programme, which covers all projects related to the intelligence community.
The post also oversees the US Intelligence Community, the grouping that combines the independent work of 16 agencies, including the CIA.
Who is Dan Coats?
Dan Coats entered Congress in 1981, representing Indiana in the House. He took Dan Quayle's place in the Senate in 1989 when Mr Quayle became President George HW Bush's vice-president.
Mr Coats had earlier served in the US Army in the 1960s and left the Senate in 1998, becoming US ambassador to Germany in the early 2000s.
After that he became a lobbyist for pharmaceutical, defence and energy companies, returning to the Senate in 2010. He did not seek re-election in 2016.
During his time in the Senate he sat on the intelligence committee.
What's his relationship with Mr Trump?
Has not always been easy.
In early 2016 he said: "I am increasingly concerned by Donald Trump's statements and behaviour, and I have serious concerns about his ability to win the general election and provide presidential leadership."
He was also damning about Mr Trump's lewd comments on women from 2005 that were leaked to the press during the election campaign.
On 8 October, he wrote on Twitter that "Donald Trump's vulgar comments are totally inappropriate and disgusting, and these words have no place in our society".
And back in December 2015, when Mr Trump announced his plans to prevent Muslims immigrating to the US, Mr Coats wrote: "Once again, Donald Trump has chosen bombastic rhetoric over sound judgement."
Generally, however, he supported his party's nominee once chosen, publicly criticising former candidate Ted Cruz for refusing to endorse Mr Trump.
What about Russia?
Mr Coats pressed President Barack Obama to punish Russia harshly for its annexation of Crimea.
As a result, Mr Coats was among several lawmakers banned from travelling to Russia.
The matter is key given the new intelligence report that says the Kremlin developed a "clear preference" for Mr Trump during the election.
It said Russia's goals were to "undermine public faith" in the US democratic process and "denigrate" his Democrat opponent Hillary Clinton.
After being briefed on the findings, Mr Trump stopped short of accusing Russia of interfering, saying only that the election outcome was not affected.
So why choose Mr Coats?
The answer may lie not with Mr Trump, but his running mate, vice-president-elect Mike Pence.
Mr Pence was the governor of Indiana - Mr Coats's state.
The two men know each other well - so well that Mr Coats was the senator who seconded Mr Pence's nomination for the Republican vice-presidential candidacy.