The former Hartlepool player displayed his versatility in numerous positions during a 12-year career at Victoria Park where he made over 500 appearances.
Humphreys, now 35, had been on trial with the Spireites after being released by Pools and impressed boss Paul Cook enough to secure a contract.
"I'm really excited at the prospect of a fresh challenge," Humphreys told Chesterfield's official website.
"I've been so impressed with the players, management team and facilities at the club and I can't wait to get started.
"This is a fantastic football club and I can't wait to get started."
Cook added: "Ritchie's had a good career and we're delighted he's agreed to join us.
"He has trained with us and showed great professionalism with a superb attitude to training. He'll offer cover in various positions."