Messi relocated to Spain from Argentina aged 13 to join Barcelona, for whom he made his competitive debut aged 17 in October 2004. He established himself as an integral player for the club within the next three years, and in his first uninterrupted season in 2008–09 he helped Barcelona achieve the first treble in Spanish football; that year, aged 22, Messi won his first Ballon d'Or. Three successful seasons followed, with Messi winning four consecutive Ballons d'Or, making him the first player to win the award four times. During the 2011–12 season, he set the La Liga and European records for most goals scored in a single season, while establishing himself as Barcelona's all-time top scorer. The following two seasons, Messi finished second for the Ballon d'Or behind Cristiano Ronaldo (his perceived career rival), before regaining his best form during the 2014–15 campaign, becoming the all-time top scorer in La Liga and leading Barcelona to a historic second treble, after which he was awarded a fifth Ballon d'Or in 2015. Messi assumed captaincy of Barcelona in 2018, and won a record sixth Ballon d'Or in 2019. Out of contract, he signed for French club Paris Saint-Germain in August 2021, spending two seasons at the club and winning Ligue 1 twice.
An Argentine international, Messi is the country's all-time leading goalscorer and also holds the national record for appearances. At youth level, he won the 2005 FIFA World Youth Championship, finishing the tournament with both the Golden Ball and Golden Shoe, and an Olympic gold medal at the 2008 Summer Olympics. His style of play as a diminutive, left-footed dribbler drew comparisons with his compatriot Diego Maradona, who described Messi as his successor. After his senior debut in August 2005, Messi became the youngest Argentine to play and score in a FIFA World Cup (2006), and reached the final of the 2007 Copa América, where he was named young player of the tournament. As the squad's captain from August 2011, he led Argentina to three consecutive finals: the 2014 FIFA World Cup, for which he won the Golden Ball, the 2015 Copa América, winning the Golden Ball, and the 2016 Copa América. After announcing his international retirement in 2016, he reversed his decision and led his country to qualification for the 2018 FIFA World Cup, a third-place finish at the 2019 Copa América, and victory in the 2021 Copa América, while winning the Golden Ball and Golden Boot for the latter. For this achievement, Messi received a record-extending seventh Ballon d'Or in 2021. In 2022, he led Argentina to win the 2022 FIFA World Cup, where he won a record second Golden Ball, became the first player to score in every stage of a World Cup (including two in the final), and broke the record for most games played at the World Cup (26).
Messi has endorsed sportswear company Adidas since 2006. According to France Football, he was the world's highest-paid footballer for five years out of six between 2009 and 2014, and was ranked the world's highest-paid athlete by Forbes in 2019 and 2022. Messi was among Time's 100 most influential people in the world in 2011, 2012 and 2023. In 2020 and 2023, he was named the Laureus World Sportsman of the Year, with Messi being the first footballer and the first team-sport athlete to win the award. In 2020, Messi became the second footballer and second team-sport athlete to surpass $1 billion in career earnings.
Messi was born on 24 June 1987 in Rosario, Santa Fe, the third of four children of Jorge Messi, a steel factory manager, and his wife Celia Cuccittini, who worked in a magnet manufacturing workshop. On his father's side, he is of Italian and Spanish descent, the great-grandson of immigrants from the north-central Adriatic Marche region of Italy, and on his mother's side, he has primarily Italian ancestry. Growing up in a tight-knit, football-loving family, "Leo" developed a passion for the sport from an early age, playing constantly with his older brothers, Rodrigo and Matías, and his cousins, Maximiliano and Emanuel Biancucchi, both of whom became professional footballers. At the age of four he joined local club Grandoli, where he was coached by his father, though his earliest influence as a player came from his maternal grandmother, Celia, who accompanied him to training and matches. He was greatly affected by her death, shortly before his eleventh birthday; since then, as a devout Roman Catholic, he has celebrated his goals by looking up and pointing to the sky in tribute to his grandmother.
"When you saw him you would think: this kid can't play ball. He's a dwarf, he's too fragile, too small. But immediately you'd realise that he was born different, that he was a phenomenon and that he was going to be something impressive."
– Newell's Old Boys youth coach Adrián Coria shares his first impression of the 12-year-old Messi.
A lifelong supporter of Newell's Old Boys, Messi joined the Rosario club when he was six years old. During the six years he played for Newell's, he scored almost 500 goals as a member of "The Machine of '87", the near-unbeatable youth side named for the year of their birth, and regularly entertained crowds by performing ball tricks during half-time of the first team's home games. However, his future as a professional player was threatened when, aged 10, he was diagnosed with a growth hormone deficiency. As his father's health insurance covered only two years of growth hormone treatment, which cost at least $1,000 per month, Newell's agreed to contribute, but later reneged on their promise. He was scouted by Buenos Aires club River Plate, whose playmaker, Pablo Aimar, he idolised, but they declined to pay for his treatment. His goalscoring idol growing up was Ronaldo, with Messi calling him "the best forward I've ever seen".