The lefty-swinging Gwynn had a career .338 batting average, won eight National League batting titles, and played in the franchise's only two World Series.
He had been signed to a one-year contract extension as the baseball coach at San Diego State on June 11. He had been on medical leave since late March while recovering from cancer treatment. He took over the program at his alma mater after the 2002 season.
Tony Gwynn, who banged out 3,141 hits during a Hall of Fame career spanning 20 seasons with the San Diego Padres, has died of cancer at age 54, it was announced Monday.
Gwynn, nicknamed "Mr. Padre" for his service to both the team and the city, was inducted into the Pro Baseball Hall of Fame in his first year of eligibility in 2007. His No. 19 was retired by the Padres in 2004.
He hit safely in 75 percent of the games in which he played during his career, and he batted .300 in each of his last 19 seasons, a streak second only to Ty Cobb.
He also was named to 15 All-Star teams, won seven Silver Slugger Awards and five Gold Glove Awards. His eight batting titles tied for second-most in MLB history.