Mirfin, 32, helped the Iron to the League One play-offs and played in their semi-final loss to Millwall.
"We were in a queue to speak to David. He is an outstanding centre-back," Stags boss Steve Evans said.
Hunt, 26, left Chester after two years with the National League club, having played 39 league games last term.
Like Mansfield's other eight summer signings to date, the lengths of their contracts have not been disclosed.
Find all the latest football transfers on our dedicated page.
Mansfield have signed defenders David Mirfin and Johnny Hunt on free transfers after their departures from Scunthorpe and Chester respectively.