Sokratis Papastathopoulos has joined Olympiakos on a deal until 2023 after his Arsenal contract was mutually terminated.
The 32-year-old joined the Gunners in July 2018 and was the third major signing of Unai Emery's reign, coming a day after the acquisitions of Stephan Lichtsteiner and Bernd Leno.
The centre back had a good start to life in north London, making 40 appearances in all competitions in his debut season at the club as Arsenal finished fifth and reached the Europa League final.
However, the arrival of Mikel Arteta in December 2019 made the Greece international's position more uncertain as he started just four league games in the rest of the season and saw his regular run in the side during the triumphant FA Cup campaign slowly peter out, coming off the bench on 89 minutes in the 2-1 win in the Final against Chelsea in August.
The final nail in the coffin for Sokratis' Arsenal career came early this season when, like Mesut Ozil, he was omitted from the team's Premier League and Europa League squads, with the former Borussia Dortmund man's only appearance against senior opposition so far in 2020-21 coming in Arsenal under-21s' 3-0 defeat to AFC Wimbledon in the EFL Trophy last month, with his deal at the club up at the end of the campaign anyway before it was terminated.
After his departure, Sokratis said: 'One of the most enjoyable times in my career ended today.
'It has been an honour to wear the Arsenal shirt and I want to thank all the coaches, team-mates, staff and fans around the world for the love and respect they have given me.
'I gave everything for Arsenal and Arsenal also gave me a lot. I wish you all the best health and success always. Thank you.'
Sokratis joins Olympiakos with the club gearing up for a Europa League round-of-32 clash against PSV Eindhoven as they chase a domestic double for the second successive season.
Pedro Martins' men lead the league by 11 points from AEK Athens and are 3-0 up against Pantelikos in the sixth round of the Greek Cup.
Notable players in Olympiakos' ranks include former Bayern Munich right back Rafinha, ex-Rennes and Inter Milan midfielder Yann M'Vila, one-time Watford and Roma left back Jose Holebas and former Marseille midfielder Mathieu Valbuena.