The 42-year-old, a skilled left-handed batsman who scored over 10,000 international runs across three formats, played a key part in India's ODI World Cup win in 2011.
Jay Shah, secretary of the Board of Control for Cricket in India (BCCI), said when he named Gambhir as coach on Tuesday that he had "endured the grind" of a long playing career -- and was the "ideal person to steer Indian cricket forward".
Most recently, he coached Kolkata Knight Riders to the IPL crown.
But initially after retiring from playing in 2018, Gambhir entered politics.
In 2019, he was elected as a lawmaker for Prime Minister Narendra Modi's Hindu-nationalist party, before quitting politics in March of this year to coach the IPL's Knight Riders.
Now he takes India's top cricket job, succeeding Rahul Dravid who stepped down after celebrating victory in the T20 World Cup -- their first global title since the 2013 Champions Trophy.
"He has that fire in him," wicketkeeper-batsman Dinesh Karthik said on Indian website Cricbuzz, adding that he will "infuse the winning culture" he brought to Kolkata.
"Being part of the national team and that patriotism that he has... India will do very well under him."
Kohli rivalry
On the field, Gambhir was a run machine.
His international career lasted between 2003 to 2016, playing his last Test in Rajkot against England.
He is the only Indian -- and one of four international cricketers including Don Bradman, Jacques Kallis and Mohammad Yousuf -- to have scored centuries in five successive Test matches.
Cricket is a lucrative business in the world's most populous nation -- home to 1.4 billion people -- and the coach's post comes under intense pressure and scrutiny on and off the field.
Crucially, Gambhir has close ties with Modi's Bharatiya Janata Party (BJP), which exerts a strong grip over the BCCI board.
"The current BCCI is the first Indian cricketing administration which is under the control of a single political party, and not a general clutch of politicians," veteran cricket journalist Sharda Ugra said.
The ex-BJP lawmaker is close to BCCI chief Jay Shah, himself the son of interior minister Amit Shah, Modi's right-hand man -- and who Gambhir said he went to visit ahead of his selection interview.
But despite his coaching track record in the IPL, some have expressed concerns regarding his volatile on-the-pitch past.
That includes the sensational IPL drama in 2013 in a face-off with rival Virat Kohli -- a superstar cricketer he will now mentor -- when the pair had to be separated by other players after clashing.
Last year, the duo faced off in another charged IPL match, but later shook hands and made up.
Kohli, as well as World Cup-winning skipper Rohit Sharma and all-rounder Ravindra Jadeja, retired from T20 internationals after their victory last month, but will stay on in ODI and Test formats.
'Want to win'
Paddy Upton, former India mental conditioning coach, wrote in his 2019 book "The Barefoot Coach" of his experience of working with Gambhir, saying that he was all too often "negative and pessimistic" as well as "insecure".
"At the same time, he was undoubtedly one of the best and most determined and successful Test batsmen in the world," Upton added.
He has also often appeared bitter -- criticising India's media for what he believed was the exaggeration of skipper M.S. Dhoni's role in the 2011 World Cup final victory over Sri Lanka.
Indian broadcasters repeatedly showed Dhoni's winning six to clinch their second ODI crown -- a decider where Gambhir smashed 97 in the winning chase in a 109-run stand with Dhoni.
Gambhir, speaking to reporters years after the match, called the World Cup a "team effort" that was "never won because of just one six".
However, pundits have never doubted Gambhir's cricketing nous, especially after he led Kolkata to two IPL titles as captain in 2012 and 2014.
India's ex-skipper Sourav Ganguly told the Times of India newspaper that Gambhir would be a "good coach", adding: "You can see the hunger, the passion and the want to win."
