Whitey Ford, the pitching ace of baseball’s New York Yankees, whose craftiness befuddled some of the best hitters of his time as he led his team to six World Series titles and 11 American League championships in the 1950s and 1960s, died Oct. 8 at his home in Lake Success, N.Y. He was 91.

The Yankees announced his death. The New York Daily News reported that he had dementia.

Mr. Ford, the winningest pitcher on the winningest baseball team of his generation, was among the last survivors of a Yankee dynasty whose baseball dominance has since gone unmatched. He was cocksure and intense — some said arrogant — on the pitcher’s mound, armed with a baffling arsenal of fastballs, curveballs, sliders and, he later admitted, spitballs.

Ted Williams, the famed slugger of the Boston Red Sox, called Mr. Ford one of the five toughest pitchers he ever faced. “You never see anything good to hit,” said Brooks Robinson, the Hall of Fame third baseman of the Baltimore Orioles.

Mr. Ford was inducted into the National Baseball Hall of Fame in Cooperstown, N.Y., in 1974, the same year as his longtime teammate Mickey Mantle. During their years together with the Yankees, Mr. Ford and Mantle were sometimes known for their off-field antics, especially in the company of Billy Martin, a fiery infielder who later managed the Yankees five times. Mr. Ford insisted that his nightlife never interfered with his performance and that he was always sober and well rested on the days he pitched.

By baseball standards, Mr. Ford was not a big man, at 5-foot-10 and about 180 pounds. His strategy was to outsmart hitters, not to overpower them. As a left-hander, he had deceptive pickoff moves that made base runners timid when contemplating a steal of second.

More than once, he spoke of the three ingredients that contribute to the making of a good pitcher: “Arm, heart and head. Arm and heart are assets, head a necessity.”

During his 16 seasons with the Yankees, Mr. Ford had a record of 236 wins and 106 losses — still the most victories of any Yankee pitcher in history. His winning percentage of .690 was among the highest in history. Except for Clayton Kershaw, a current star with the Los Angeles Dodgers, Mr. Ford’s lifetime earned run average of 2.75 is the lowest of any starting pitcher whose career began after 1920.

For more than a decade, Mr. Ford was the finest pitcher on powerful Yankee teams that included such Hall of Famers as Mantle in center field, shortstop Phil Rizzuto and catcher Yogi Berra. On Berra’s death in 2015, Mr. Ford replaced him as holder of the honorary title of “greatest living Yankee,” according to New York Times sports columnist George Vecsey. Berra’s predecessors as the greatest living Yankees were Joe DiMaggio and Babe Ruth.

Mr. Ford had a stellar rookie season in 1950, finishing with a 9-1 record and an ERA of 2.81. He started Game 4 of the 1950 World Series against the Philadelphia Phillies and entered the ninth inning with a 5-0 lead.

But, thanks to a flyball lost in the sun by Yankee outfielder Gene Woodling, the Phillies rallied to make the score 5-2. With two outs, two men on base and the tying run at-bat, Manager Casey Stengel emerged from the Yankee dugout to make a pitching change and was greeted with a chorus of boos. Mr. Ford wondered why the fans were booing him before realizing that the boos were directed at Stengel for taking him out of the game.

Allie Reynolds relieved Mr. Ford and got the final out to secure the Yankees’ World Series victory. In the New York Times the next day, sports columnist Arthur Daley wrote that Mr. Ford had the “brass of a burglar.”

After the season ended, Mr. Ford was drafted and would miss the next two seasons while serving in the Army. He rejoined the Yankees in 1953.

Three times, in 1955, 1961 and 1963, Mr. Ford led the American League in victories. He twice led the league in earned run average, recording ERAs of 2.47 in 1956 and 2.01 in 1958. His best year may have been in 1961, when he went 25-4 and won the Cy Young Award, at a time when it was given to only one pitcher in the major leagues. He had another outstanding season in 1963, when he was 24-7 with a 2.74 ERA.

In World Series competition, Mr. Ford won a record 10 games and lost eight, which also was a record. He was named the most valuable player of the 1961 World Series, in which the Yankees defeated the Cincinnati Reds in five games.

That year, Mr. Ford established a World Series record for most consecutive innings pitched without allowing a run. The previous record had been held by Babe Ruth, when he was a pitcher for the Boston Red Sox. After he became an outfielder for the Yankees, Ruth slugged 60 home runs in 1927 — a mark eclipsed by the Yankees’ Roger Maris, also in 1961.

“It’s been a bad year for the Babe,” Mr. Ford said.

Edward Charles Ford was born in New York City on Oct. 21, 1928. His father, a semipro baseball player, worked for the Consolidated Edison power company and later ran a bar in the Astoria neighborhood of Queens. His mother was a bookkeeper.

Mr. Ford witnessed his first Yankees game when he was 8, and on summer nights, he played sandlot baseball until dark. Because his neighborhood high school in Queens did not have a baseball team, he attended an aviation trades high school in Manhattan.

After graduating in 1946, the small but strong-armed lefty had offers from the Boston Red Sox and the New York Giants but signed with the Yankees, the team he had rooted for since childhood. He played for Yankee farm teams until he was called up to the major leagues midway through the 1950 season.

One of his minor league managers called him “Whitey” for his blond hair. Over the years, Mr. Ford would acquire other nicknames, including “Chairman of the Board” for his leadership, and “Slick” for his late-night ways.

Mantle, Martin, Mr. Ford and other Yankee players made headlines in 1957 in what has become known as the Copacabana incident. The players had gathered to celebrate Martin’s birthday at the Manhattan nightclub, where events got out of hand. After a brawl, six Yankees were fined, and Martin was promptly traded to Kansas City.

For Mr. Ford and Mantle, there would be other such nights during their playing years and beyond.

“I guess Mickey and I overdid it,” Mr. Ford confessed at a 1994 old-timers day at Yankee Stadium. By then, he had quit drinking, Mr. Ford said. Mantle, who underwent treatment for alcohol abuse, died in 1995 at 63.

After a series of shoulder injuries and circulatory problems in his pitching hand, Mr. Ford had his first losing season in 1966. He tried to come back in 1967 but lasted less than two months. Unwilling to struggle in mediocrity, he abruptly walked off the mound during a game and retired at the age of 38.

Mr. Ford later told interviewers that he sometimes threw spitballs and nicked, muddied, scraped or otherwise tampered with baseballs to make his pitches harder to hit.

“I didn’t begin cheating until late in my career, when I needed something to help me survive,” he admitted in a 1987 autobiography, “Slick: My Life In and Around Baseball.”

“I didn’t cheat when I won the twenty-five games in 1961. I don’t want anybody to get any ideas and take my Cy Young Award away. And I didn’t cheat in 1963, when I won twenty-four games. Well, maybe a little.”

In 1951, Mr. Ford married Joan Foran. They had three children. A son, Tommy Ford, died in 1999. A complete list of survivors could not be confirmed.

After he retired, Mr. Ford spent one season as the Yankees’ first-base coach, then left baseball for a period before returning as a pitching coach in 1974. His No. 16 uniform was retired that year.

He later served as a pitching instructor for the Yankees during spring training, invested in harness racing and owned a restaurant. In 2008, Mr. Ford auctioned off many items from his baseball career, including his 1961 World Series most valuable player trophy, a 1950 Yankees jersey and a baseball signed by President John F. Kennedy during a White House visit.

In 2001, Mr. Ford co-wrote a book with sportswriter Phil Pepe, “Few and Chosen: Defining Yankee Greatness Across the Eras,” in which he selected Lefty Gomez as the all-time greatest Yankee left-handed pitcher.

Asked why he had chosen Gomez over himself, Mr. Ford replied, “I lied.”