Slutsky, 46, replaced Marco Silva at the KCOM Stadium in June but won only four of his 19 Championship games in charge.
Saturday’s draw at Sheffield Wednesday left the Tigers, relegated from the Premier League last season, 20th in the table, three points above the bottom three.
Hull vice-chairman Ehab Allam said: “Leonid has worked tirelessly in his role and has acted with complete honour and been a pleasure to work with.
“Unfortunately results have not improved as both parties would have hoped and therefore it was agreed for the relationship to come to an end.
24. Portsmouth: 21,100
“Hull City sack manager Leonid Slutsky”
“I would like to thank Leonid and Oleg for their efforts here and sincerely wish them well for the future.”
While Slutsky was “proud” to have taken on the challenge at Hull.
On his departure, the former CSKA Moscow boss said: “I would like to really thank everyone associated with Hull City from the players and staff to the owner and especially the fans.
“I am very proud to have been through this experience, it was challenging but a very exciting time for me.
“Hull City will always be a part of my heart and I wish the team all the very best for the future.”