The 24-year-old is the son of former Leeds, Bradford Northern and Featherstone Rovers hooker Trevor Clark.
Born in Pontefract during his father’s spell playing in England, Mitch Clark began his career with Australian club Penrith Panthers, playing a key part in their under-20s’ Holden Cup Grand Final victory in 2013.
He joined Doncaster in 2015 – making 23 appearances in his only campaign at the South Yorkshire club – and moved to Bradford Bulls the following season.
Clark scored five tries in 24 appearances for Bulls in 2016 and played 15 times for Hull KR this year.
He is the second member of Rovers’ 2017 squad to join Tigers in as many days, following half-back Jamie Ellis.
“I can’t wait to rip into pre-season,” Clark said.
“I was born in Pontefract and to get to play for this club and to play for [coach] Daryl Powell is such a massive opportunity for me.
“I just can’t wait to get started.”
Powell added: “Mitch Clark is a player I have known for a long time, having discussed his future with him three years ago.
“I’m delighted he has signed for Castleford at this time as I believe he has a big future with us.
“He is an all-action front-rower who has great leg speed when carrying the ball and real intent when he is defending
“I welcome Mitch to the club and look forward to working with him.”
A statement from Rovers said: “Hull Kingston Rovers can confirm that prop Mitch Clark has been released from his contract with the club and will move to Castleford Tigers from 2018.
“Clark joined the Robins from Bradford Bulls 12 months ago and went on to make 15 appearances as the club secured promotion to the Betfred Super League, but was unable to claim a regular spot in the team.
“Clark’s departure provides the club with a non-federation trained place to bring in another overseas player as recruitment for 2018 continues.
“Hull Kingston Rovers would like to thank Mitch for his efforts in red and white and wish him all the best at the Tigers.”