Hunt and Gilham played 13 and 15 games for the Giants respectively, but both made their names previously at Geelong and Hawthorn.
Hunt played in the 2007 and 2011 Cats' premiership wins, managing 198 games in all as a reliable rebounding defender.
Gilham played 98 games for the Hawks and his full back role was critical in the Hawks' 2008 premiership victory, after one game at Port Adelaide.
The pair told teammates of their decision on Tuesday morning, with Hunt urging his teammates to make the most of their careers.
"It flies by, three years ago I was getting a premiership medal and thinking I have 10 years to go. It catches up with you pretty quick(ly) and this year has been amazing and I’ve loved every second of it," Hunt said.
Gilham thanked the Giants for their support over the journey.
"It's been a great journey for me over the past 12 years to be involved at three clubs at the AFL level," Gilham said.
"I've been battling the last few years with injury and that’s the reason why I decided half way through the year this would be my last season."
