“I want to thank the board, the players and all of the staff for their support and commitment during four wonderful years where I have developed as a coach and as a person.”
A Hull KR statement, external read: “Willie will leave with the very best wishes of everyone at the club after four years of being the most successful coach in our modern history, taking us to the very pinnacle of the sport as world champions.”
Hull KR hold all four major titles available to Super League clubs after beating Brisbane Broncos to win the World Club Challenge in February.
They had gone 40 years without a league title before they beat Wigan Warriors in the Grand Final in October.
They also won the Challenge Cup – for the first time since 1980 – and the League Leaders’ Shield.
Since last year Peters has combined his Hull KR job with being assistant coach of Australia.
Last month he said he was interested in taking over as England head coach after Shaun Wane stepped down.
Eighth in the Super League table after five games this season, Hull KR face rivals Hull FC on Friday.