O'Neal was born on March 6, 1972 in Newark, New Jersey, to Lucille O'Neal and Joseph Toney, an All-State guard in high school who was offered a basketball scholarship to play at Seton Hall. Toney struggled with drug addiction and was imprisoned for drug possession when O'Neal was an infant. Upon his release, he did not resume a place in O'Neal's life and instead agreed to relinquish his parental rights to O'Neal's stepfather, Phillip A. Harrison, a career Army Reserve sergeant.^[5][6] O'Neal remains estranged from his biological father; he and Toney have never spoken, and O'Neal has expressed no interest in establishing a relationship.^[6] On his 1994 rap album, Shaq Fu: The Return, O'Neal voiced his feelings of disdain for Toney in the song "Biological Didn't Bother", dismissing him with the line "Phil is my father."

O'Neal credits the Boys and Girls Club of America in his hometown of Newark, New Jersey, with giving him a safe place to play and keeping him off the streets. "It gave me something to do," he said. "I'd just go there to shoot. I didn't even play on a team."^[7] He led his Robert G. Cole High School team, from San Antonio, Texas, to a 68–1 record during his two years there and helped the team win the state championship during his senior year.^[8] His 791 rebounds during the 1989 season remains a state record for a player in any classification.^[9]

On January 31, 2012, O’Neal was honored as one of the 35 Greatest McDonald's All-Americans.^[10]O'Neal became a free agent after the 1995–96 NBA season. In the summer of 1996, O'Neal was named to the United States Olympic basketball team, and was later part of the gold medal-winning team at the 1996 Olympics in Atlanta. While the Olympic basketball team was training in Orlando, the Orlando Sentinel published a poll that asked whether the Magic should fire Hill if that were one of O'Neal's conditions for returning.^[20][21] 82% answered "no".^[20] O'Neal had a power struggle while playing under Hill.^[22][23] He said the team "just didn't respect [Hill]."^[24] Another question in the poll asked, "Is Shaq worth $115 million?" in reference to the amount of the Magic's offer. 91.3% of the response was "no".^[21][22] O'Neal's Olympic teammates rode him hard over the poll.^[21][23] He was also upset that the Orlando media implied O'Neal was not a good role model for having a child with his longtime girlfriend with no immediate plans to marry.^[20] O'Neal compared his lack of privacy in Orlando to "feeling like a big fish in a dried-up pond."^[25] O'Neal also learned that Hardaway considered himself the leader of the Magic and did not want O'Neal making more money than him.^[26] On the team's first full day at the Olympics in Atlanta, it was announced that O'Neal would join the Los Angeles Lakers on a seven-year, $121 million contract.^[27][28] He insisted he did not choose Los Angeles for the money. "I'm tired of hearing about money, money, money, money, money," O'Neal said after the signing. "I just want to play the game, drink Pepsi, wear Reebok," he added, referring to a couple of his product endorsements.^[29][30] The Lakers won 56 games during the 1996–97 season. O'Neal averaged 26.2 points and 12.5 rebounds in his first season with Los Angeles; however, he again missed over 30 games due to injury. The Lakers made the playoffs, but were eliminated in the second round by the Utah Jazz in five games.^[31] In his first playoff game for the Lakers, O'Neal scored 46 points against the Portland Trail Blazers, the most for the Lakers in a playoff game since Jerry West had 53 in1969. On December 17, 1996, O'Neal shoved Dennis Rodman of the Chicago Bulls; Rodman's teammates Scottie Pippen and Michael Jordan restrained Rodman and prevented further conflict. The Los Angeles Daily News reported that O'Neal was willing to be suspended for fighting Rodman, and O'Neal said: "It's one thing to talk tough and one thing to be tough."^[32]

The following season, O'Neal averaged 28.3 points and 11.4 rebounds (1997-1998). He led the league with a 58.4 field goal percentage, the first of five consecutive seasons in which he did so. The Lakers finished the season 61–21, first in the Pacific Division, and were the second seed in the western conference during the 1998 NBA Playoffs. After defeating the Portland Trail Blazers and Seattle SuperSonics in the first two rounds, the Lakers again fell to the Jazz, this time in a 4–0 sweep.^[33]

With the tandem of O'Neal and teenage superstar Kobe Bryant, expectations for the Lakers increased. However, personnel changes were a source of instability during the 1998–99 season. Long-time Laker point guard Nick Van Exelwas traded to the Denver Nuggets; his former backcourt partner Eddie Jones was packaged with back-up center Elden Campbell for Glen Rice to satisfy a demand by O'Neal for a shooter. Coach Del Harris was fired, and former Lakers forward Kurt Rambis finished the season as head coach. The Lakers finished with a 31–19 record during the lockout-shortened season. Although they made the playoffs, they were swept by the San Antonio Spurs, led by Tim Duncan and David Robinson in the second round of the Western Conference playoffs. The Spurs would go on to win their first NBA title in 1999.