John Egerton, Campbell's longtime friend, said Campbell had been in failing health since a stroke in 2011 and died from complications related to it.
Campbell was an influential voice, calling for integration in the South while also ministering to those who opposed it, persuading, gently, for a more tolerant society. His work gained praise from former President Jimmy Carter among many others.
The (Nashville) Tennessean noted Campbell's mantra: "If you're gonna love one, you've got to love 'em all."
He was also a staunch advocate for ending the death penalty and abortion.
Egerton wrote Campbell's passing came as partial relief for those who loved him after struggling in poor health for two years.
"In a final act of benevolence, Will spared them all the anguish of a long and traumatic last watch," Egerton wrote. "For him and for his family, his departure was not a cry of despair; it was more like a whispered sigh of relief. Finally, he is at peace."
Campbell's remains will be cremated and a memorial service in Nashville will be scheduled for later this month, Egerton said.