Clough, 33, has made more than 300 career appearances for St Helens, Bradford, Huddersfield and Widnes.
Clough said: “After a 17-year career in the sport and over 350 professional games, the time has come to hang up my boots at the end of this season and retire from rugby league.
“Each year the demands on my body are increasing, and ultimately this has informed my decision to announce my retirement once the 2021 season comes to an end.
“I’d like to take this opportunity to thank all of the clubs who have given me the opportunity to realise my dream of making a career from the sport I love. Thanks also to all the coaches I have played under, all of the players I have shared the field with and all of the supporters who have welcomed me at each club I have represented. Thanks also goes to RL Cares for their support during my career and for helping me plan for life after rugby league.”
Cook said: “Having had the amazing privilege of getting to play out my childhood dream these past 18 years, the time has finally come for me to hang up my boots.
“I want to start by giving a shoutout to RLCares who have been supporting me tremendously these last few years to prepare for life after rugby.
“To everyone else who has supported me on my journey I would also like to take this opportunity to say thank you.”