He was 77.
Morgan died at his home in Danville, California, a suburb of San Francisco, on Sunday, according to a family spokesman.
"The Reds family is heartbroken," Reds CEO Bob Castellini said in a statement. "Joe was a giant in the game and was adored by the fans in this city."
The Oakland native was named National League MVP in 1975 and 1976, leading Cincinnati to World Series titles in both those seasons.
He was inducted into baseball's Hall of Fame in 1990, following a 22-season career with the Houston Colt .45s, Reds, San Francisco Giants, Philadelphia Phillies and Oakland A's.
The 10-time All-Star Game selection was an all-around offensive force, smacking 268 home runs and stealing 689 bases. He also had a keen eye at the plate, forcing pitchers to walk him 1,865 times, which boosted his career on-base percentage to .392.
Morgan was also a wizard on defense, winning five Gold Glove awards as his league's best-fielding second baseman.
The lineup of Cincinnati's "Big Red Machine" teams were filled with fearsome hitters Morgan, Pete Rose, Johnny Bench, Tony Perez and George Foster and defensive stalwarts like Dave Concepcion and Cesar Geronimo.
The 1975 World Series is best known for Carlton Fisk’s home run off the left-field foul pole that won Game 6 for the Boston Red Sox. An NBC camera dramatically captured Fisk wildly waving his arms, begging for the ball to stay fair.
But it was Morgan who delivered the decisive championship-winning blow, with an RBI single in the ninth inning to break a 3-3 tie in Game 7. That run-scoring hit brought home teammate Ken Griffey, the father of future Hall of Fame inductee Ken Griffey Jr.
This article originally appeared on NBCNews.com.