Sunil Chhetri was born on 3 August 1984 to K. B. Chhetri, an officer in the Corps of Electronics and Mechanical Engineers of the Indian Army, and Sushila Chhetri in Secunderabad, Telangana, India. His father played football for the Indian Army’s team while his mother and her twin sisters played for the Nepal women’s national team. Chhetri started playing football from a young age taking part in various tournaments.

On 30 March 2004, Chhetri played his first game for the Indian U-20 team in the 1–0 victory over Pakistan U-23 team in the 2004 SAF Games in Pakistan. On 3 April 2004, Chhetri scored twice for the Indian U-20 team against Bhutan U-23 team in their 4–1 victory. On 12 June 2005 Sunil scored his first goal for the senior India national football team against Pakistan.

In 2005, Chhetri signed for JCT for the 2005–06 season. During that season, Chhetri scored three goals. He scored twice against Salgaocar before the third came against Sporting Goa, as JCT finished the season that year in sixth place. Meanwhile, in the Santosh Trophy, Chhetri scored two hat-tricks for Delhi in the group stages of the 61st Santosh Trophy against both Orissa and Railways. However, despite Chhetri’s best efforts, Delhi were eliminated in the pre-quarter final round after losing 1–0 to Tamil Nadu in extra time.

Then, during the very first season of the I-League, Chhetri scored seven goals as JCT finished the season in third place. His only brace that season came against Salgaocar during the final match of the season. Midway through that season though, in December 2007, Chhetri was awarded the AIFF Player of the Year award for 2007 for his excellent form and performances for his club and country.

Chhetri’s first international tournament was the 2007 Nehru Cup. In the opening game, India defeated Cambodia 6–0 with Chhetri scoring two goals. He also scored a goal in the 2–3 defeat to Syria and another in the 3–0 win over Kyrgyzstan to take his goal tally to four. Chhetri was involved in the build-up to N.P. Pradeep’s decisive goal as India beat Syria 1–0 in the final to become the first champions of the tournament since 1997. Later in 2007, India began their 2010 FIFA World Cup qualification campaign. They were knocked out in the first round by Lebanon with Chhetri scoring once in the away leg (a 4–1 defeat) and once in the home leg (a 2–2 draw) resulting in a 6–3 aggregate defeat.

In October 2008 it was rumored that Chhetri had sparked interest from foreign clubs. These clubs were Leeds United of the Football League One and Estoril Praia of the Liga de Honra, the second division of Portugal. During an interview Chhetri said that “Nothing has been confirmed as yet but yes, I think I am close to getting there.” indicating that there was a chance of him signing in England. However, in the end, a move never materialized.

Before the 2008–09 season began, Chhetri signed with fellow I-League side East Bengal. He scored on his debut for East Bengal against Chirag United on 26 September 2008 in which he scored in the 28th minute as East Bengal won the match 3–1.

The 2008 SAFF Championship started with three victories out of a possible three in the group stages. In the opening game, Chhetri scored a goal in a 4–0 victory over Nepal. He scored once more in the championship—in the 2–1 semi-final victory over Bhutan; this was an equaliser before Gouramangi Singh scored India’s second goal to send India through to the final. India lost 1–0 to the Maldives in the final and Chhetri played for the full 90 minutes. Later that year, in the 2008 AFC Challenge Cup, Chhetri played in all of the matches and scored four goals. In the 1–0 win over Afghanistan, he was involved in the build-up to Climax Lawrence’s goal. He also played for the full 90 minutes against Tajikistan (a 1–1 draw) and Turkmenistan (a 2–1 win). In the semi-final against Myanmar, Chhetri scored the only goal in a 1–0 victory after being assisted by Baichung Bhutia to see India through to the final. In the final against Tajikistan, Chhetri scored a hat-trick which enabled India to win the Cup. This automatically qualified India for the 2011 Asian Cup, the first time they had qualified for the tournament in 24 years. His first goal was originally disallowed for offside by Uzbek referee Valentin Kovalenko, who changed his mind after consulting his assistant. Hundreds of fans waited outside the stadium to greet India’s new “poster boy” and India manager Bob Houghton stated, “He is remarkable, brave and honest. He never gives up.”

Midway through the season though, reports came out suggesting that two Major League Soccer teams were interesting in Chhetri, along with his international teammate Steven Dias. These two MLS sides were rumored to be the Los Angeles Galaxy and D.C. United. However, on 25 January 2009, Chhetri arrived in Coventry, England to begin a trial at Coventry City of the Football League Championship, thus rejecting MLS. Four days later though, Coventry City manager Chris Coleman said that they would not be following their interest in Chhetri. Four months later though, Chhetri said that he would go back to Coventry City in June 2009 for another extended trial. That never materialized however.

Upon being released by East Bengal, Chhetri signed a two-year contract with another fellow I-League side, Dempo on 22 May 2009. In his contract was a clause which allowed him to leave for trials abroad in the future if he wanted to.

On 7 August 2009 it was reported that Scottish Premier League side Celtic were linked with a move to sign Chhetri. The Scottish club had watched Chhetri during a pre-season friendly with Santboià, a Segunda División B side, in a pre-season fixture. Yogesh Joshee, Chhetri’s agent, was quoted as saying, “I’m waiting to get feedback from Celtic, who saw him on Monday by head scout and then another scout came to watch game, I’ll let you know the outcome when I know.”

Then on 30 August 2009 it was announced by the Hindustan Times that Chhetri had signed a three-year contract with English Football League Championship side Queens Park Rangers but that he was denied a work permit by the British government. According to an article on the Football Players’ Association of India’s official website, Chhetri was denied a work permit because India were not in the top 70 of the FIFA World Rankings. Chhetri, however, remained positive: “But it’s not the end of the world. I will still continue to work hard for my country and my club Dempo, who have been very supportive.”

In March 2010 it was announced that Chhetri was on trial with the Kansas City Wizards of Major League Soccer and that he had played during their pre-season games. He then formally signed for the team on 24 March 2010, becoming just the third Indian to play outside of South Asia and the first Indian to play in MLS. Peter Vermes, the head coach of the Wizards, was quoted as saying “One thing we really like about Sunil is that he’s a crafty player. Technically he’s very sharp, and he’s a guy that has good attacking tendencies.”

On 14 April 2010 Chhetri made his debut for the Wizards in the Lamar Hunt U.S. Open Cup qualification play-in game against the Colorado Rapids in which he started but ended up with a yellow card and was substituted out of the game at half-time as Kansas City lost the match 1–2. Then, on 23 July 2010, it was announced that Chhetri would play in a mid-season friendly against Manchester United. However this caused controversy as he had not yet played a league match. On 25 July 2010, Chhetri made an appearance for the Wizards against United, coming on as a substitute for Teal Bunbury in the 69th minute as Kansas City won the match 2–1.

However, the next day, it was announced that Chhetri was to compete for the Indian national team until the end of the 2011 AFC Asian Cup. Then on 5 February 2011 it was announced that Chhetri had officially left the team.

On 10 February 2011, it was announced that Chirag United had beaten United Sikkim to the signing of Sunil Chhetri for the rest of the 2010–11 I-League season. On 3 April 2011, Chhetri scored his first goal for Chirag United against Dempo, however, Dempo won the match 4–2. Chhetri then scored a brace on 29 April 2011 against ONGC to help salvage a 2–2 draw for Chirag.

On 22 July 2011, it was announced by I-League club Mohun Bagan that Chhetri has signed a one-year deal with the club.

Initially, Goal.com stated that Chhetri would miss the 2009 Nehru Cup through injury. He played in the tournament, however, and he scored in the second match of the Nehru Cup, a penalty in a 2–1 win over Kyrgyzstan, this being first time he had completed a full match since getting injured before the pre-season tour of Spain with his club. He featured in the other three games in the round robin stage of the tournament, including the “dress rehearsal” for the final against Syria, but did not score. Chhetri was one of India’s scorers in the penalty shootout victory over Syria in the final after the match had ended in a 1–1 draw. He showed flashes of brilliance and scored the second goal in a 5–2 defeat at the hands of Bahrain in the 2011 Asian Cup. He also scored a goal against South Korea at the 2011 AFC Asian Cup.

He was named the national team Captain for the 2012 AFC Challenge Cup qualification which took place in Malaysia. On 16 November 2011 Chhetri scored in the 39th and 53rd minute for India against Malaysia in a friendly match played at the Salt Lake Stadium. The match ended 3–2 in favour of India. On 11 December 2011 after scoring a goal in SAFF Cup’s final he set a new record by scoring seven goals in a single edition of the SAFF Championship surpassing I.M.Vijayan’s record of six goals in the 97 edition.

On 4 July 2012, it was reported that Chhetri had signed a two-year contract with Sporting Lisbon and would play in their reserve team. He then made his debut for the side in a Segunda Liga match against S.C. Freamunde in which he came on in the 85th minute as Sporting CP B won the match 2–0.

On 22 August 2012, Chhetri scored a goal with a header in the added time of the first half against Syria in the first match of 2012 Nehru Cup where India won the match 2–1. In the second match, which was on 25 August he scored two goals against Maldives, one goal coming from penalty where the team won 3–0. In the final against fancied opponents Cameroon, Chhetri scored from a well-taken penalty kick to equalize the score at 2–2. In the ensuing penalty shootout which India won 5–4, Chhetri went as the second kick-taker from India and scored.

On 13 February 2013, it was announced that in order to get more playing time Chhetri would be loaned out to Churchill Brothers in the I-League for the remainder of the season. He made his debut for Churchill Brothers on 26 February 2013 against Kitchee in the AFC Cup in which Chhetri started as Churchill Brothers lost 0–3. He then scored his first goal for Churchill Brothers in their next match against Semen Padang on 12 March 2013 in which he started and scored in the 27th minute as Churchill Brothers drew the match 2–2. After the season ended, Chhetri had scored four goals in eight matches as he helped Churchill Brothers to their second ever I-League title.

On 19 July 2013, following his release from Sporting Lisbon, Chhetri signed with new direct-entry I-League side Bengaluru for the 2013–14 season. He made his debut for the club in their opening game on 22 September 2013 against Mohun Bagan in which he came on as a 46th-minute substitute for Beikhokhei Beingaichho as Bengaluru managed a 1–1 draw. Chhetri then scored his first goal for the side in the next game against Rangdajied United in which he found the net in the 67th minute as Bengaluru won 3–0.

He did not score again for Bengaluru till November when, on the 2nd against Mumbai, Chhetri scored from the penalty-spot in the 57th minute to help Bengaluru FC to a 2–2 draw. He then scored his first brace of the season against on 1 December 2013 against Shillong Lajong in which his 7th and 34th-minute strikes helped the team to a 2–1 victory. Then in the next match against former club Churchill Brothers Chhetri scored another brace as he led Bengaluru FC to a 3–1 victory. He then scored his third brace in a row in the very next match against Mohammedan as he led Bengaluru FC to a 3–2 win in Kolkata.

Chhetri then finished off an impressive first half of the season for Bengaluru with a goal from the penalty spot against Salgaocar, his ninth of the season, as he led the Bangalore side to a 2–1 victory. He then scored another goal in the teams very first Federation Cup match against Sporting Goa as Bengaluru FC won 5–3 on 15 January 2014. With 14 goals and 7 assist in 23 appearances in the season, Chhetri led Bengaluru FC to their first ever I-League title in its debut season.

Chhetri began the season in the 2014 Durand Cup, playing and scoring three times but missed the penalty in the shoot-out in the semi-final against Salgaocar which turned out to be the decisive penalty miss as Bengaluru crashed out.

Chhetri was picked up by Mumbai City during the 2015 Indian Super League for Rs. 1.2 crores, making him the most expensive Indian player at the auctions. He missed his team’s first and second round matches in the 2015 season through national team commitments, playing against Turkmenistan and Oman in Group D of the 2018 World Cup qualifiers, but returned against Chennaiyin in a 2–0 loss. He scored twice in his second game of the season against Roberto Carlos lead Delhi Dynamos in a 2–0 win, the first for his team in the season before scoring again, from the penalty spot, in the very next game against then table toppers Goa managed by Zico. Chhetri made history, becoming the first Indian player to score a hat-trick, in his fourth game of the season, against NorthEast United and taking his total of the season to 6 goals in 4 games. he was the top scorer for Mumbai City for that season as he poached 7 Goals. fast forward to 2018 he was still the pole position of All-time top scorers for Mumbai City FC. he came back in Mumbai colors for 2016’s ISL season, the team done well this time as they reached playoffs for first time, but national commitments & less game time with the likes of Diego Forlan & Sony Norde kept him away from score sheet. After two seasons with the islanders, he signed a three-year contact which made him the highest-paid Indian Player in 2017.

Chhetri was loaned out to Bengaluru for the 2015–16 I-League season, where he ended up scoring 5 times in the league, thus helping his team win the league title for the second time in three years. He also scored twice in a round of 16 match against Kitchee in the 2016 AFC Cup, helping his side to an unlikely 2–3 win away from home. This would be the first time Bengaluru had reached the quarter finals of the tournament.

On 9 June 2016, Bengaluru announced that Chhetri had signed a one-year contract at the club, thus reverting his ownership rights to the club from Mumbai City. Chhetri scored twice as Bengaluru won the 2016 AFC Cup Semi Final tie by beating Johor Darul Ta’zim in Bengaluru. Chhetri’s second goal was a 30-yard strike, where he received the ball from C.K. Vineeth, beat one defender and unleashed a screamer to give Bengaluru the lead.

On 11 October 2017, Chhetri scored and assisted in a 4–1 home win against Macau in the 2019 AFC Asian Cup qualifiers, with this win they qualified for the 2019 AFC Asian Cup after missing out in 2015. Chhetri captained India to a 13 match unbeaten run before losing the final match to Kyrgyzstan. Nonetheless, not only did India qualify for the 2019 AFC Asian Cup but also managed to top their group. He was among four renowned Asian players including Ali Daei, Sun Jihai and Phil Younghusband to be chosen for the seeds for the upcoming Asian cup.

On 4 December 2017, Chhetri married his long time girlfriend Sonam Bhattacharya who is the daughter of the former Indian national football player and Mohun Bagan legend Subrata Bhattacharya. He signed a 3-year deal with global sports giant PUMA India starting from 2020.

In June 2018, Chhetri scored a hat-trick in a 5–0 win over Chinese Taipei in their first match of 2018 Intercontinental Cup. However, after this match, Chhetri was disappointed with the poor turnout at the stadium and he uploaded a video on Twitter requesting people to come to Mumbai Football Arena to support the Indian team. His video went viral and garnered widespread support from fans, celebrities and legendary cricketers like Sachin Tendulkar and Virat Kohli. The stadium was packed with exuberant crowd for the rest of the matches. In the second match of the tournament, which was also Chhetri’s 100th international appearance for India and also scored two goals including a goal from penalty spot in a 3–0 victory over Kenya. Chhetri scored a goal in the next match against New Zealand, but the match ended 2–1 loss for India though India qualified for the final. On 10 June, Chhetri scored twice again in a 2–0 win over Kenya in the final to win the Intercontinental Cup title and also equalled Argentina’s Lionel Messi’s tally of 64 international goals, making him the joint-second active international goalscorer at that time behind Portugal’s Cristiano Ronaldo who had 81 goals. He finished as the top scorer of the tournament with eight goals.

On 15 October 2019, Chhetri has become the only Indian to secure a place in the list of top 10 footballers who have scored maximum goals in international football.