The Giants announced that Simmons had died "peacefully," saying, "The Giants family and Bay Area sports community lost a true gentleman."
Simmons was one of the original voices of the Giants when they moved West in 1958, and he covered Hall of Famers Willie Mays and Willie McCovey, Juan Marichal, Gaylord Perry and Orlando Cepeda.
"Like many fans, my earliest Giants memories were listening to Lon and Russ on my transistor radio," Giants President and CEO Larry Baer said. "Hearing his broadcasts ignited my and thousands of others' passion for Giants baseball. He will be deeply missed by all of us."
Simmons broadcast Oakland's victory in the earthquake-interrupted 1989 Bay Bridge World Series, with that booming voice, announcing, "The A's have won the World Series in a sweep!"
The A's noted that Simmons "called some of the greatest moments in Oakland history, including the final three outs of the A's 1989 World Series championship."
"His humility and humor made him one of the most beloved figures in franchise history, which makes today such a sad day for A's fans and baseball fans around the world," the team said in a statement. "Lon was an incredible broadcaster, but his personality and wit set him apart as one of the game's all-time greats."
Over three stints with the Giants, Simmons considered one of his greatest thrills getting to call Mays' 600th home run. His signature phrase on the longball became, "Tell it goodbye!"
"If they had a Nobel Prize for baseball, Willie would have won it," Simmons said during Mays' 80th birthday festivities in May 2011.
He also announced many of home run king Barry Bonds' drives during his pursuit.
"R.I.P #LonSimmons you will forever be in our hearts. Broadcasting Bay Area sports since 1958," Bonds posted on Twitter.
But Simmons, who was honored with the Ford C. Frick Award by the Hall of Fame in 2004, also had a famous call on Hall of Fame quarterback Steve Young's epic, back-and-forth game-winning scramble for 49 yards against the Minnesota Vikings on Oct. 30, 1988, that still lives in the memories of Bay Area sports fans.
"Young, back to throw, in trouble, he's going to be sacked. No, gets away, he runs, gets away again, goes to the 40, gets away again, to the 35, cuts back at the 30, to the 20, the 15, the 10. He dives. Touchdown, 49ers!"
49ers CEO Jed York said the team "was deeply saddened to lose one of our own today with the passing of Lon Simmons."
"Much more than an iconic voice in the great history of Bay Area sports, Lon shared his passion for this region's teams with generations of fans. For more than two decades 49ers fans were treated to the great talents of a man of high integrity and tremendous humility," York said. "Whether it was a game-winning touchdown pass from Joe Montana to John Taylor or the miraculous scramble by Steve Young against the Vikings, he brought some of our greatest moments to the world."
Ahead of the Niners' final season at Candlestick Park in 2013, Simmons reflected on the run-down stadium where he did most of his work. Simmons often took shots at himself and that humor became part of his charm, along with his baritone voice and personable nature.
"I felt that Candlestick and I were soul mates: We were both big and ugly, we were both windy and they could never figure out how to get rid of either one of us," Simmons said. "As John Brodie used to say about Candlestick, he said, 'We have the advantage when we play at home, I have the advantage because I've played in the wind and things and I know what the ball's going to do.' The guys come in to play one game a year and the winds and stuff killed them because it really did affect the ball throwing it."
Simmons — who spent much of his time in the radio booth alongside Russ Hodges — dealt with cancer more than once in recent years. He requested not to have a memorial service, the Giants said. He attended selected games last season and still worked as a community ambassador for the Giants after retiring in 2002.
"I'm grateful for the support of the Bay area fans," Simmons said upon being selected winner of the Ford C. Frick Award. "The fans are more important to me than anything else because those are the people I tried to please the 40 years."