Bob Gibson, a Hall of Fame baseball pitcher whose fierce glare and blazing fastball intimidated hitters for nearly two decades and whose overwhelming dominance in 1968 with the St. Louis Cardinals contributed to changes in the sport’s rules, died Oct. 2 in Omaha. He was 84.

He died 52 years to the day after he set a World Series record of 17 strikeouts in a game. The death was confirmed by Brian Bartow, a Cardinals spokesman. The cause was pancreatic cancer, which had been diagnosed in 2019.

Mr. Gibson, a right-handed pitcher who briefly played basketball for the Harlem Globetrotters, was known as one of the game’s most intense competitors during his 17 years in the major leagues.

With his cap pulled low across his forehead, Mr. Gibson had a menacing, truculent mound presence. He refused to speak to opposing players and often brushed hitters off the plate when he thought they were getting too comfortable.

“Bob wasn’t just unfriendly when he pitched,” former teammate and Hall of Fame manager Joe Torre once told the New York Times. “I’d say it was more like hateful.”

During an era when baseball had such star pitchers as Sandy Koufax, Juan Marichal, Jim Palmer, Ferguson Jenkins and Tom Seaver, Mr. Gibson was among the best. He won at least 20 games in a season five times and led the Cardinals to three World Series, winning two. He is ranked by baseball historians as one of the top 15 pitchers in history.

At 6-foot-1 and about 190 pounds, Mr. Gibson was not especially big, but his arsenal included an excellent fastball and a hard, sweeping slider. He wasted no time between pitches and delivered the ball with such force that his follow-through carried him off the mound toward the first base line, his arms and legs extended in every direction.

His 1968 season, in which he had a record of 22 wins and nine losses and a minuscule earned run average of 1.12, the lowest in baseball since 1914, is considered one of the game’s greatest achievements.

He led the National League in strikeouts, with 268 and had 28 complete games, and his 13 shutouts were the most in baseball since 1916, when the game was still in its low-scoring “dead-ball” era. During one 95-inning stretch, he allowed only two earned runs.

Mr. Gibson won both the Cy Young Award as the league’s best pitcher and the Most Valuable Player Award, leading his Cardinals into the World Series against the Detroit Tigers. In the opening game of the series, he had 17 strikeouts, setting a record that still stands.

His longtime catcher, Tim McCarver, later honored by the baseball Hall of Fame as a broadcaster, recalled Mr. Gibson’s 17th strikeout, as Tigers slugger Willie Horton took a called third strike to end the game.

“I heard him let out a frightened gasp,” McCarver wrote in his 1998 book, “Tim McCarver’s Baseball for Brain Surgeons and Other Fans,” “because he thought that ball was going to hit him. It must have broken eighteen inches in order to cross the plate.”

The ’68 World Series featured Mr. Gibson and the Tigers’ Denny McLain, whose 31-6 record made him the first pitcher to win 30 games in a year since Dizzy Dean in 1934. Mr. Gibson beat McLain twice before losing in the seventh and decisive game, 4-1, to Detroit left-hander Mickey Lolich.

With the performances of McLain, Mr. Gibson and the Los Angeles Dodgers’ Don Drysdale — who set a record (later broken) with 58⅔ consecutive scoreless innings — the 1968 season became known as the “year of the pitcher.” Major League Baseball then instituted what some called the “Gibson rules,” reducing the size of the strike zone and lowering the height of the pitcher’s mound from 15 inches to 10.

The changes had little effect on Mr. Gibson, who won 20 games, with a 2.18 ERA in 1969. The next year, he went 23-7 and won his second Cy Young Award.

Mr. Gibson retired in 1975 with a career record of 251-174, a 2.91 ERA and 56 shutouts. He was the first National League pitcher — and the second in history, after the Washington Senators’ Walter Johnson — with 3,000 strikeouts, finishing with 3,117.

He was elected to the National Baseball Hall of Fame in his first year of eligibility, becoming only the second African American pitcher to be enshrined. The first was Satchel Paige, who spent most of his career in the old Negro leagues.

Mr. Gibson found success against a backdrop of social unrest, particularly in 1968, when the Rev. Martin Luther King Jr. and Sen. Robert F. Kennedy (D-N.Y.) were assassinated. Although he was not an activist in the civil rights movement, he was conscious of his position as an African American in his sport and in society.

“Gibson was always acutely aware of the different reactions of people to Bob Gibson the professional baseball player, and Bob Gibson the black man,” author David Halberstam wrote in “October 1964,” about that year’s World Series. “He never lost his wariness, and indeed, the more successful he became, the warier he became.”

Some teammates and sportswriters believed Mr. Gibson was redirecting his anger at racial prejudice into his pitching, but he disagreed.

“When I was pitching out there I was pitching with the will to win,” he told the Chicago Tribune in 1994, “and rage had nothing to do with it.”

Pack Robert Gibson was born Nov. 9, 1935, in Omaha, the youngest of seven children. He was named after his father, who died before his son was born. His mother worked in a laundry.

An older brother introduced Mr. Gibson to sports, and he excelled in baseball, basketball and track. At Creighton University in Omaha, Mr. Gibson became the first Black player on the baseball and basketball teams.

He led the basketball team in scoring and rebounding and set a school career record of 20.2 points per game. His uniform — No. 45, the same number he wore with Cardinals — was the first to be retired at Creighton.

He left college in 1957, signing a professional baseball contract with St. Louis and a basketball contract with the Harlem Globetrotters. He played both sports for a year before concentrating on baseball.

In Omaha, Mr. Gibson had attended integrated schools and did not encounter overt segregation until he played for a Cardinals minor league club in Georgia. When he made it to the major leagues in 1959, he said, his manager, Solly Hemus, did not hide his contempt for Black players.

“Either he disliked us deeply,” Mr. Gibson wrote in a 1994 autobiography with Lonnie Wheeler, “Stranger to the Game,” “or he genuinely believed that the way to motivate us was with insults.”

After Hemus was replaced by Johnny Keane in 1961, Mr. Gibson began to flourish. Keane put him in the starting rotation and cultivated a team spirit that looked beyond race.

McCarver, the Cardinals’ young catcher, grew up in Memphis as a White Southerner. He once boarded the team bus with an ice-cream cone. (Some accounts say it was a bottle of soda.) Mr. Gibson tested his teammate by asking whether he could have a lick from the cone. McCarver stammered that he’d “save some” for him and later said the incident — and his subsequent friendship with Mr. Gibson — helped him overcome his “latent prejudices.”

On the field, Mr. Gibson helped lead the Cardinals to a World Series victory over the New York Yankees in 1964, winning the series MVP award.

He was having an excellent year in 1967 when he was struck on the shin by a line drive off the bat of the Pittsburgh Pirates’ Roberto Clemente. Mr. Gibson pitched to three more batters before collapsing on the mound with a broken leg.

After two months, Mr. Gibson returned to action in September, leading the Cardinals into the 1967 World Series against the Boston Red Sox. He won the first, fourth and seventh games and was named World Series MVP for a second time.

The Cardinals retired Mr. Gibson’s No. 45 jersey at the end of his career, but with no job offers in St. Louis, he returned to Omaha, where he opened a restaurant, owned a radio station and advertising company, and was board chairman of a bank in the city’s African American community.

In the early 1980s, his onetime teammate Torre hired Mr. Gibson for coaching jobs with the New York Mets and Atlanta Braves. Beginning in 1995, Mr. Gibson spent several years as a coach and broadcaster for the Cardinals.

His first marriage, to Charline Johnson, ended in divorce. Survivors include his wife since 1979, the former Wendy Nelson of Bellevue, Neb.; two daughters from his first marriage; and a son from his second marriage.

Tales of Mr. Gibson’s intimidating manner on the mound circulated among players and fans long after he retired.

“He’d knock down his own grandmother if she dared to challenge him,” slugger Hank Aaron once told the Boston Globe. “Don’t stare at him, don’t smile at him, don’t talk to him. He doesn’t like it.”

The stories were known to everyone, it seemed, except Mr. Gibson.

“I didn’t see myself as intimidating when I was pitching,” he told the Tribune. “Certainly if I had known that when I was pitching, I would have been more nasty than I was.”