This is Andrés Manuel López Obrador, also known as "AMLO." The 64-year-old emerged as the country's president on Sunday night with around 53% of the vote.
He grew in a middle-class family in Tabasco state, the son of a petroleum merchant during Mexico's oil boom. His friends at the time thought he too would become a businessman, but he chose to become a political activist and a human rights lawyer fighting against big oil companies in his 20s instead.
On December 1, he will take over from Enrique Peña Nieto, who leaves the presidency with a mere 17% approval rating, and who clashed with Donald Trump over trade and the proposed US-Mexico border wall.
López Obrador inherits a country plagued with organized crime, deadly violence, drug wars, and widespread corruption among law enforcement.
next slide will load in 15 secondsSkip AdSkip AdPeña Nieto's struggle to handle the disappearance of 43 students in 2014 stoked massive protests against Mexico's violence and official corruption.
López Obrador's campaign of ending corruption, reducing violence, and addressing poverty, therefore, was immensely popular among voters. The president-elect has vowed to overthrow the "mafia of power," which he said has looted the country.
He even vowed to slash his own salary and raise those of lowly-paid government workers, and sell the presidential plane — which is valued at about $580 million.
Source: The New York Times
He has also vowed to live in his own house, and turn Mexico's presidential palace into an art center.
López Obrador's success "are not endorsements of ideologies, but rather demands for change" from a country that has grown disillusioned with the status quo, said Laura Chinchilla, the ex-president of Costa Rica.
Similarly, Shannon O'Neil, senior fellow for Latin America Studies at the Council on Foreign Relations, said: "He's been able to capture the mantle of the person who's on the outside who wants change."
Source: The New York Times, Associated Press
next slide will load in 15 secondsSkip AdSkip AdLópez Obrador previously described Donald Trump as "erratic and arrogant," and said the US president's plans to build a wall "goes against humanity, it goes against intelligence and against history."
Last year, he even wrote a book titled "Oye, Trump" — or "Listen Up, Trump" — in which he railed against what he called "hispanophobia" in the US.
He also said he would propose to keep NAFTA, which Trump has said he was "not happy with." But López Obrador "doesn't want to be the President who kowtows to President Trump," said Duncan Wood, director of the Wilson Center's Mexico institute.
Wood told CNN: "He doesn't want to be the President who kowtows to President Trump. He doesn't want to be the President who sells out national pride. He wants to be a president who stands up to the United States.
"He wants to be a President who says, 'we deserve and we demand respect.'"
Source: CNN, The Washington Post
Jeremy Corbyn, the leader of Britain's Labour Party and López Obrador's friend, also tweeted on Monday: "Today brings a new beginning for México."
This was his third time running for president, having lost the past two elections in 2006 and 2012. After losing the 2006 election, he called the results a fraud and called himself "the legitimate president of Mexico" and his supporters staged sit-ins and blockades around the country.
next slide will load in 15 secondsSkip AdSkip AdIn 2012, López Obrador claimed electoral fraud after losing to Peña Nieto — López Obrador received 31.6% of the vote, while Peña Nieto got 38.2%. Mexico's electoral tribunal recounted the votes but confirmed the original result.
Lopez Obrador said: "I confess that I have a legitimate ambition: I want to go down in history as a good president of Mexico. I desire with all my soul to raise the greatness of our country on high."