Bennett heads to the Liberty Stadium after making 92 appearances in gold and black, playing an integral role in winning the Championship title in 2017/18.
Wolves are not receiving any money up front for the 30-year-old centre-half, who joined on a free transfer in the summer of 2017 after his release from Norwich.
The deal, though, does include appearance and promotion bonuses while getting him off the wage bill.
Young defender Sanderson, meanwhile, is off to Sunderland for the season after agreeing a new two-year Wolves contract.
Centre forward Ennis will also spend 2020/21 in League One, with Burton Albion.