The 30-year-old Rioli was contracted until the end of next year but opted to retire.
"I have given all I can to the game at the highest level," Rioli said in a club statement.
"I made up my mind a couple of weeks ago that this would be my last season.
"I want to see even more opportunities given to our young, talented small forwards at Port Adelaide in Joe Berry and Tom Cochrane.
"They're the future of our club. It's time for me to step aside."
The Power on Monday delisted utility Jeremy Finlayson, injury-prone defender Ryan Burton and fringe players Dylan Williams, Hugh Jackson and Lachie Charleson.
They were axed axed at exit meetings overseen by new head coach Josh Carr, who has taken over from Ken Hinkley.
Rioli considered retiring in the midst of controversies in late April and early May.
The goalsneak expressed a hatred for Hawthorn in the wake of the rival club's racism allegations in a social media post in late April.
And in early May, he was banned for one game for a social media threat to Bailey Dale after the Western Bulldog made what Port described as a culturally insensitive remark during a game.
Rioli played 109 AFL games - 57 at Port and 52 at West Coast, where he was part of the Eagles' 2018 premiership.
In July, he told a club podcast he carried a weight of past indiscretions including his 18-month suspension from 2019 for trying to swap his marijuana-tainted urine sample with a clean sample in a drug test when at West Coast.
The talented attacker announced his retirement as the 28-year-old Burton and 29-year-old Finlayson were among players delisted.
Halfback Burton arrived after three seasons at Hawthorn for the 2019 season and Finlayson crossed from GWS at the end of 2021.
Burton's career stalled amid frequent injuries, with the halfback playing only eight AFL games this season.
The 162-gamer suffered a knee injury in round 16 and didn't feature again.
Finlayson, who also played just eight AFL games this year for a career total of 128, fell from selection favour in an inconsistent season.
Their departures open up further list spots at Port, who have also farewelled retiring club legend Travis Boak.
Ex-Adelaide and Gold Coast utility Rory Atkins, who joined the Power this season, has also retired.
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