Lingard made 65 appearances for the K League side, scoring 18 goals, after he joined the South Korean side in February 2024 in what is one of the club’s biggest ever signings.
The ex-Manchester United star wrote on Instagram:
"My time in South Korea has been unbelievable - the football, the atmosphere and the passion around this club have been top class. The love, support and the appreciation you have shown towards me for these last two years has been truly amazing.
"I'll always be grateful for the opportunity to play for such a massive club."
Thanking the Englishman for his commitment to the club, FC Seoul said:
"He generated an extraordinary level of public attention and emerged as a symbolic figure not only for the club but for the entire K League."
The former England star is set to make his final appearance for the side in their AFC Champions League Elite match against Melbourne City next week in what will be an emotional goodbye.
He is now set to become a free agent once again just in time for the January transfer window where reports are already linking him back to the Premier League.