Dave Matthews will also be on hand for the Oct. 2 show at Miller Park, home of Major League Baseball's Brewers.
"This anniversary concert is a chance for everyone to join with Farm Aid to support the family farmers who are growing hope for America, through the good food they produce, the economies they build, and their care for the soil and water," Nelson said in a statement. "Family farmers are the backbone of our country, and right now we need them more than ever." This year's event will be broadcast live on DirecTV.
Nelson, Mellencamp, Young and Matthews have headlined every Farm Aid going back to 2001, but the quartet is always joined by special guests, who will be announced in the coming weeks. Last year's concert featured appearances from Wilco, Jason Mraz, Jamey Johnson and others.
Mellencamp and Nelson made the announcement this afternoon on Ustream, with Nelson donning a Brewers jersey and mistakenly referring to them as the "Braves," according to Rolling Stone. The Braves actually left Milwaukee for Atlanta in 1965, and the former Seattle Pilots came to town in 1970, rechristened the Brewers.
"Willie ought to get the Nobel Peace Prize for Farm Aid," Mellencamp said. "Willie is the guy who deserves all the credit for Farm Aid.
Farm Aid started in 1985, spurred by a comment Bob Dylan made at Live Aid earlier in the year.
"I hope that some of the money...maybe they can just take a little bit of it, maybe...one or two million, maybe...and use it, say, to pay the mortgages on some of the farms and, the farmers here, owe to the banks," Dylan said.
Since its inception, Farm Aid has raised more than $37 million to help stabilize family farms, according to its official website.