England captain George Williams will face future Dolphins coach Kristian Woolf when England meets Tonga in a Rugby League World Cup clash before they join forces in 2027.
Williams will move to the Dolphins on a two-year contract, strengthening their halves alongside Tongan international Isaiya Katoa and Brad Schneider.
The 31-year-old has played more than 350 first-grade matches across the NRL and Super League, starring for Canberra Raiders and Warrington Wolves.
Since his Test debut in 2015, Williams has become a mainstay of England's side and was appointed captain in 2023.
He will also reunite with England representatives Herbie Farnworth and Morgan Knowles, his former international teammates.
Dolphins chief executive Terry Reader said the signing marked a significant step forward for the club.
"George is one of the most accomplished halves in the game and to have someone of his experience and leadership joining the Dolphins is a huge boost for the squad," Reader said.
"He has performed at the highest level in both the NRL and Super League and has proven himself as a leader on the international stage with England."
"George brings a strong kicking game, competitiveness and a wealth of experience that will complement the players we already have within the spine."
"We're really excited about the opportunity to bring George to the Dolphins and to see what he can add alongside Isaiya, Brad and the rest of the squad from 2027."