The attacking midfielder left United a year ago as a free agent, stating he was not given the game time he believed that he deserved.
After signing a short-term deal with Forest, Lingard was again out of favour for most of the season.
He started only 12 games in the Premier League and barely featured since the turn of the year.
On Instagram, Lingard wrote: "Thank you to everybody @officialnffc from the fans to all the backroom staff and of course the players.
“Been a rollercoaster journey but we stuck together through thick and thin and achieved our goal. It's been a pleasure.''