Romeu, 34, will depart the club for a second time when his contract expires at the end of this month, after the club decided not to extend his contract.
The Saints hero made just seven appearances during his second stint at St Mary’s, having re-joined the club as a free agent in November.
Romeu, who also played twice for the under-21s during the 2025/26 season, has been linked with a move to Japanese football ahead of officially departing Saints.
Before his next step is confirmed, Romeu has written a message to Southampton supporters, wishing them all the best for the future.
On social media site X, he wrote: “It was so good to see you all again. Thank you for making me feel so loved and respected during my second spell at the club.
“I’ll always be grateful for your support. Wishing you all the very best, always.”
Romeu, a Champions League winner with Chelsea, has played 263 times for Southampton across his two spells, scoring eight goals.