Huddersfield fans had been hoping that Kongolo would extend his stay in England after helping them secure Premier League football for another season.
However, the Netherlands defender now looks set to return to France after posting a message on social media in which he bids farewell to the West Yorkshire club.
"Thanks to all of you for having me at this great club," Kongolo wrote on Instagram.
"I'll always remember the support you gave me, I wish you all the best of luck next season and know for sure Huddersfield will always remain in the PL. Love the song you guys sang for me, the best I heard at least."
Kongolo, who has been capped three times by the Oranje, is contracted to Monaco until June 2022.