Chapman was born in Holguín, Cuba, on February 28, 1988. He lived in a three-room house with his parents and two sisters. Chapman’s father was a boxing trainer and then later worked for the city. His mother did not work outside the home. Chapman’s paternal grandparents had emigrated from Jamaica to Cuba in order to get a better education, The Chapmans, whose last name can be traced to English settlers in Jamaica in the late 1600s, were not a prominent family.

A friend of Chapman invited him to join a local baseball team at the age of 15. He began playing as a first baseman until the coach noticed that Chapman could throw well enough to become a pitcher, which Chapman began in 2003.

Chapman joined the Holguín Sabuesos of the Cuban National Series League in 2006. In 327⁄3 career innings, Chapman compiled a 24–19 win–loss record, a 3.74 earned run average (ERA), and 365 strikeouts. He was used mainly as a starting pitcher, although he made 11 relief appearances in the 2007 season.

After a failed attempt to defect in the spring of 2008, Chapman reported to Havana to meet with Cuban president Raúl Castro who gave him a conditional reprieve, suspending him for the remainder of the National Series season and also keeping him off Cuba’s national team for the 2008 Summer Olympics but allowing him to return to the National Series and play in the WBC in 2009.

Chapman successfully defected from Cuba while in Rotterdam, Netherlands where the Cuban national team was participating in the World Port Tournament on July 1, 2009; Chapman walked out the front door of the team hotel and entered into an automobile driven by an acquaintance. Gerardo Concepción defected from the Cuban national team in the same tournament. Chapman eventually established residency in Andorra and petitioned MLB to be granted free agent status.

On January 10, 2010, Chapman agreed to a long-term contract with the Cincinnati Reds. The Reds announced that they had signed Chapman to a six-year contract, worth $30.25 million according to MLB sources. The Associated Press reported that the bonus totals $100.25 million, paid annually over 11 years, with an additional bonus if he became eligible for salary arbitration in 2012 or 2013.

Chapman made his Major League debut August 31, 2010, in the eighth inning against the Milwaukee Brewers; his first pitch was clocked at 98 mph (158 km/h) as a called strike (which was promptly tossed to the dugout by catcher Ryan Hanigan, to be saved). In nine pitches he retired the side. He recorded his first Major League win on September 1 after pitching an inning of relief against the Brewers. Chapman threw the fastest pitch recognized by MLB on September 24, 2010, at Petco Park in San Diego, California. It was clocked at 105.1 mph to Tony Gwynn Jr. in the eighth inning.

With a three-quarters delivery, Chapman throws four pitches: a four-seam fastball averaging 99–100 miles per hour (159–161 km/h), a slider averaging 87–88 miles per hour (140–142 km/h), a splitter, and a change-up. His fastball averaged 100.3 miles per hour (161.4 km/h) in 2010, but that declined to 98.6 miles per hour (158.7 km/h) in 2011 and 97.8 miles per hour (157.4 km/h) through August 2012. This more modest speed might have been part of an attempt to better control his fastball. By 2015 Chapman’s fastball averaged 99.98 miles per hour (160.90 km/h). That same year, Statcast revealed that Chapman threw the 62 fastest pitches of the season, topping out at 103.92 miles per hour (167.24 km/h).

On September 24, 2010, against the San Diego Padres, Chapman was clocked at 105.1 mph (169.1 km/h), according to PITCHf/x, the fastest pitch ever recorded in Major League Baseball. On July 19, 2016, Chapman matched his previous record of 105.1 mph with a ball to Baltimore’s J. J. Hardy. That record was tied by Jordan Hicks on May 20, 2018.

Chapman served solely as a relief pitcher in 2011, appearing in 54 regular season games and finishing the season with a 3.60 ERA. He also struck out 71 batters in just 50 innings of work that season.

On August 13, Chapman gave up a home run to Rafael Devers of the Boston Red Sox. The pitch was clocked at 103 mph, making it the fastest pitch hit for a home run in the Statcast era (breaking Kurt Suzuki’s home run off of a Chapman 102 mph pitch the previous year). It was also Chapman’s first home run given up to a left-handed batter since Luke Scott of the Baltimore Orioles did so in 2011. Later that month, Chapman gave up only his third home run off a left-hander when Yonder Alonso of the Seattle Mariners hit one of his 101 mph fastballs out. His fastest pitch of 2017 was 104.3 miles an hour, best in MLB. His four-seam fastball had the highest average speed of any MLB pitcher’s pitches in 2017, at 99.7 mph.

On April 18, 2011, Chapman threw a pitch to Pittsburgh’s Andrew McCutchen that the scoreboard at Great American Ball Park clocked at 106 mph (170.6 km/h), but the box on Fox Sports Ohio’s broadcast listed it at 105 mph (169 km/h) and the PITCHf/x system calculated a release speed of 102.4 mph (164.8 km/h). The disparity between these speeds has been widely discussed and questioned.

On July 1, 2012, Chapman was named to his first All-Star Game. Chapman won the MLB Delivery Man of the Month Award for July 2012, in which he recorded 13 saves while not allowing a run in 14 ⁄3 innings while striking out 31 batters—more than 60% of the batters he faced. It was the third month of the season in which he did not allow a single run. He was named the August Delivery Man of the Month. Chapman finished the 2012 season with a 1.51 ERA and 38 saves in 43 chances, recording 122 strikeouts and 23 walks in 71 ⁄3 innings.

Scouts worried about his control issues and lack of a solid third pitch, noting that these issues could affect his ability to be a Major League starter, but Chapman’s control seemed to improve. After issuing 41 walks in 50 innings the previous season, Chapman walked 23 batters in 2012 over 71 ⁄3 innings.

In March 2013, it was announced that Chapman would be the closer for the Cincinnati Reds. He was an All-Star selection for the second season in a row. He finished the 2013 year with 38 saves, a 4–5 record, 112 strikeouts, and a 2.54 ERA.

During a spring training game against the Kansas City Royals on March 19, 2014, Chapman was struck in the head by a line drive from Salvador Pérez. The spring-training game between the Reds and the Royals was ended at that point with Kansas City leading 8–3. Chapman underwent surgery to fix a skull fracture above his left eye. A metal plate was inserted into his head to stabilize the fracture.

Chapman began the 2014 season on the 15-day disabled list. On April 18, Chapman was cleared to begin throwing batting practice sessions. Reds manager Bryan Price said that he wasn’t sure when Chapman would throw but said it likely would be during the team’s 10-game trip that ended April 27. He was activated from the disabled list on May 10. Chapman recorded his 100th save against the Arizona Diamondbacks on July 29, 2014, becoming the eighth-fastest pitcher to reach the milestone. In the 20-pitch appearance, Chapman threw 15 fastballs, all of which were above 100 mph. In 54 appearances, Chapman produced 106 strikeouts with 36 saves going 0–3 with an ERA of exactly 2.00.

When Chapman left Cuba, he left behind his father, mother, two sisters, girlfriend Raidelmis Mendosa Santiestelas, and newborn baby, Ashanty Brianna. He reunited with them when he helped them transfer to the United States; the details of how they transferred remain confidential. On June 30, 2014, his son, Atticus Gabriel Chapman, was born in Cincinnati. In May 2012, it was reported that Chapman was being sued for allegedly serving as “an informant for Cuban state authorities after a failed defection attempt and help[ing] turn in another man in order to get back on the country’s national baseball team.”

Chapman and the Reds agreed to a one-year, $8.05 million contract on February 13, 2015. Chapman was selected to the 2015 MLB All-Star Game. He pitched a scoreless ninth inning and struck out the side on 14 pitches, 12 of which were recorded at 100 mph or greater. His fastest pitch in 2016 was 103.9 mph, best in MLB. His four-seam fastball had the highest average speed of any MLB pitcher’s pitches in 2015, at 100.0 mph. In the 2015 season, Chapman made 65 relief appearances with a 4–4 record, a 1.63 ERA, and 33 saves.

On December 28, 2015, Chapman was traded to the New York Yankees. Cincinnati received four minor league players including right-handed pitchers Caleb Cotham and Rookie Davis, and infielders Eric Jagielo and Tony Renda in the exchange. On January 11, 2016, manager Joe Girardi named Chapman the team’s new closer. He avoided arbitration on February 12, 2016, by agreeing to a one-year contract worth $11.325 million. Chapman was suspended for the first 30 games of the season due to an off-season personal conduct policy violation related to domestic violence. He made his first appearance for the Yankees on May 9, 2016 striking out 2 and allowing a run as the Yankees won 6–3 over the Kansas City Royals. On July 18 against the Orioles, Chapman threw for 105 mph twice in the top of the ninth inning, averaging 103.2 mph with his fastball.

On December 7, 2015, news broke that Chapman was involved in an alleged domestic violence incident with his girlfriend in Davie, Florida at his home on October 30, 2015. A pending trade with the Los Angeles Dodgers was put on hold as MLB announced it would investigate the incident as part of its personal conduct policy. In the incident, he was accused of pushing his girlfriend, putting his hands around her neck, and choking her; he subsequently fired eight gunshots. No charges were filed by the police due to inconsistency of the reports and insufficient evidence, and his attorney issued a statement denying the allegations. The trade to the Dodgers was canceled and the Reds traded Chapman to the Yankees three weeks later. Although he was not charged, MLB suspended Chapman for 30 games as a result of his “use of a firearm and the impact of that behavior on his partner,” ending May 9, 2016. He was the first player disciplined by the new personal conduct policy enacted in August 2015, which empowered MLB to suspend a player from games without a final sentence.

On July 25, 2016, the Yankees traded Chapman to the Chicago Cubs for Gleyber Torres, Billy McKinney, Adam Warren, and Rashad Crawford. In an interview with ESPN, Chapman stated he was thrilled that the Cubs went after him, especially considering the recent success of Héctor Rondón. Chapman made his first appearance as a member of the Cubs on July 27, pitching a 1–2–3 ninth and striking out two batters in a non-save situation. His fastest pitch in 2016 was 105.1 miles an hour, best in MLB. His four-seam fastball had the highest average speed of any MLB pitcher’s pitches in 2016, at 100.9 mph, and his two-seam fastball had the third-highest average speed, at 100.4 mph.

Chapman made three saves in four opportunities in the 2016 National League Division Series against the San Francisco Giants to tie and set new Division Series records respectively; Wade Davis tied his record in the 2017 National League Division Series, but did it in each of his opportunities.

Chapman’s workload in the 2016 World Series escalated with the Cubs facing elimination at the hands of the Cleveland Indians. Down 3–1 in the series, Chapman pitched through the seventh, eighth, and ninth innings of Game 5, allowing only one hit and preserving the Cubs’ 3–2 lead. He was called upon again in the seventh and eighth innings of Game 6, where he allowed one hit and one run en route to a 9–3 victory. Chapman appeared the next day to close out Game 7 with a 6–3 lead in the bottom of the eighth inning, but blew the save opportunity, allowing Cleveland to tie the game on a two-run homer by Rajai Davis. Chapman pitched through the bottom of the ninth to send the game into extra innings. The Cubs tallied the game-winning run in the 10th inning, making Chapman the winning pitcher and giving him his first World Series title.

On December 15, 2016, Chapman signed a five-year, $86 million contract to return to the Yankees. This was the largest contract given to a relief pitcher as of 2017.

On May 14, 2017, Chapman was placed on the 10-day disabled list due to rotator cuff inflammation in his left shoulder. Although MRIs revealed no structure damage, Chapman was ruled out for at least two weeks. On June 18, the Yankees activated Chapman from the DL and he pitched that afternoon against the Oakland A’s.

In 2018 Chapman was elected as an MLB All-Star, representing the American League. On July 13, 2018, he announced that he would skip the All Star Game to rest his knee due to tendinitis. On August 22, Chapman was placed on the 10-day disabled list due to left knee tendinitis. His fastest pitch of 2018 was 104.4 miles an hour, second-best in MLB only to pitches by Jordan Hicks. His sinker had the highest average speed of any MLB pitcher’s pitches in 2018, at 100.9 mph. In 2018, he had the lowest swing rate for his in-strike-zone sliders of any pitcher in baseball (42.5%).

In 2019, he was 3–2 with 37 saves and a 2.21 ERA, as in 60 relief appearances he struck out 85 batters in 57.0 innings (13.4 per 9 innings). Chapman logged one save in the American League Division Series and one in the American League Championship Series but gave up a walk-off home run to José Altuve with two outs in the ninth inning of Game 6 of the ALCS, eliminating the Yankees from the playoffs.

On July 11, 2020, during the COVID-19 pandemic, it was reported that Chapman had tested positive for the virus. Manager Aaron Boone announced that he was cleared to return to the team on July 31. Chapman pitched in his first major league game of 2020 on August 17. On September 2, Chapman received a three-game suspension for throwing a pitch at the head of Tampa Bay Rays batter Mike Brosseau. Brosseau later hit a game-winning home run off Chapman in Game 5 of the ALDS, effectively ending the Yankees season. His 100.5 mph-average sinker was the fastest sinker of any major league pitcher for the 2020 season.

On July 11, 2020, it was announced that Chapman had tested positive for COVID-19.

Aroldis Chapman did recover from COVID-19 and returned to baseball activities on August 17, 2020.