He died Sunday at his home in Albuquerque, New Mexico of natural causes, The Indianapolis Speedway said Monday. Unser won the Indy 500 in 1968, 1975 and 1981.
His younger brother, Al, is one of only three four-time Indy 500 winners in race history. Al Unser won the race in 1970, 1971, 1978 and 1987. The Unser family tradition stretched to Al Unser's son, Al Unser Jr., who won the Indy 500 in 1992 and 1994.
Bobby Unser was born Feb. 20, 1934, in Colorado Springs, Colorado, but moved with his family as a child to New Mexico. His father owned a garage along Route 66 and he his brother grew up tooling around in old jalopies before he began his racing career in 1949 at Roswell New Mexico Speedway.
After a two years in the U.S. Air Force from 1953 to 1955 -- a stint for which he was always proud -- Unser turned to racing full time and became one of the greatest racers in Indianapolis Motor Speedway history.
He was one of just 10 drivers to win the 500 at least three times and Unser and Rick Mears are the only drivers to win the 500 in three different decades. Unser was one of six members of the Unser family to race in the Indianapolis 500.
His final Indy 500 victory in 1981 came in a Roger Penske entry in one of the most controversial and contentious outcomes. Unser beat Mario Andretti by 5.18 seconds, but officials ruled Unser passed cars illegally while exiting the pit lane under caution -- drawing a penalty that docked him one position and moved Andretti to winner.
Penske and Unser appealed and after a lengthy process the penalty was rescinded in October of that year. It was the 35th and final victory of Unser's career.
At Indianapolis, Unser produced 10 top-10 finishes in 19 career starts. He led led in 10 races for a total of 440 laps, which to this day ranks 10th on the all-time list.
After his driving career, Unser moved to broadcasting and won an Emmy Award as part of the ABC Sports broadcast team for "Outstanding Live Sports Special" for its coverage of the 1989 Indianapolis 500.
Unser is survived by his wife, Lisa; sons Bobby Jr. and Robby; and daughters Cindy and Jeri.