Pennant bids farewell to Stoke
The 31-year-old returned to Stoke last June following the arrival of Mark Hughes as manager, having been released by Hughes's predecessor, Tony Pulis, at the end of last season.
However, he played in only 11 games this season and is now looking for a new club.
"I met with the manager and he was honest with me, which I appreciated," Pennant told British newspaper the Daily Mirror. "I wasn't playing and at 31 now, I need to be playing games.
"I'd like to thank the club for the opportunity of a new challenge and would like to thank everyone at Stoke City and the fans for the fantastic support over the last few years. I'm looking forward to the new chapter in my life."
Pennant, a former Arsenal trainee, joined Stoke from Real Zaragoza in January 2011, but he was unable to hold down a first-team place and spent part of last season on loan at Wolverhampton Wanderers.
He spent three years at Liverpool, notably playing in the 2007 Champions League final.