The 30-year-old will leave Emerald Headingley at the end of the current season.
Hall made his debut for Rhinos in 2007 and is the fifth-highest try scorer in the club’s history with 231 in 327 appearances.
He is out of contract this season and the announcement clears the way for Australian NRL club Sydney Roosters to confirm his signing.
In a statement released by Rhinos, Hall said: “I have had 12 amazing seasons as a Leeds Rhinos player and I am immensely proud of what we have achieved together.
“For me personally, I feel that this is the right time for a new challenge after such a long period at the club and my decision in no way reflects on the Rhinos.
He added: “Words cannot really do justice to how much representing my home town club and enjoying so much success has meant to me.
“My focus now is on the remainder of this season and putting the Rhinos in the best possible position for next season and beyond.
“I have had the privilege of working with brilliant coaches and players in my time at the club and I have total faith that under Kevin Sinfield and James Lowes the club will continue to go in the right direction for the future.”
Sinfield, Rhinos’ director of rugby, said: “Naturally we are disappointed to lose a player of the quality of Ryan Hall.
“The club were keen to keep him here and we made him an offer that reflected his standing in the game. I know that Ryan will be doing everything between now and the end of the season to make sure his time at the club ends on the best possible note.
“He will remain a close friend of the Rhinos. As a Leeds lad, playing for his club and winning with the Rhinos means so much to him and I am sure we will remain in regular contact with him.
“The departure of any senior player is a chance for someone else to come into our group, just as it was Ryan when he first broke through over a decade ago and we will be looking to strengthen the whole group for 2019 and beyond with this opportunity.”
A six-time Grand Final winner, Hall has also played in two successful Challenge Cup finals, being named man of the match at Wembley in 2014.
He was a try scorer in the 2012 World Club Challenge win over Manly Sea Eagles and his last-gasp touchdown at Huddersfield Giants in 2015 secured the league leaders’ shield.
Hall has touched down 35 times in 38 Tests for England.