Killebrew played 22 seasons in the Majors with the Washington Senators, Minnesota Twins, and Kansas City Royals. In 2,435 career games, he hit .256 with 573 home runs and 1,584 RBIs, and was considered one of the most feared power hitters of his era.
"Harmon Killebrew personified Hall of Fame excellence in every aspect of his dynamic life," Jane Forbes Clark, the chairman of the National Baseball Hall of Fame and Museum, says in a statement.
"He will forever be remembered for his 573 career home runs and as the 1969 American League most valuable player, and as one of the greatest hitters of his era."
Killebrew's battle with cancer became public in December. Friday, he was moved to a hospice and issued the following in a statement:
"I have exhausted all options with respect to controlling this awful disease. My illness has progressed beyond my doctors' expectation of cure."
Killebrew belted 40 home runs in a season eight times and retired as the American League career leader in home runs by a right-handed hitter. That record has since been broken by New York Yankees slugger Alex Rodriguez.
Killebrew, however, was not part of what is commonly known as baseball's "steroid era." Rodriguez, on the other hand, has admitted to using performance-enhancing drugs -- as have many modern-day players who, despite juicing, don't compare to "Hammerin' Harmon."