Kyle Sinckler has joined Toulon for next season, with his England team-mate Lewis Ludlam expected to follow.
Bristol have announced that Sinckler, 31, will leave to join the Top14 side, who also have Northampton back-rower Ludlam lined up.
The switch to the three-time Champions Cup winners will effectively end the England aspirations of both players.
Under existing rules, England head coach Steve Borthwick is unable to select players based with clubs abroad.
Toulon, who won the last of their four French titles in 2014, sit fifth in the Top 14 with seven rounds of the regular season remaining.
“They are two good signings who will complete our forward pack for many years,” Toulon club president Bernard Lemaitre told the AFP news agency.
Ludlam will link up with former Northampton team-mate Dave Ribbans, who made the same move last summer.
“They respond to the profiles we’re looking for in our recruitment,” added Lemaitre.
“We’re trying to have higher expectations on mentality, behaviour and lifestyle of players like their impressive compatriot Dave Ribbans.”
Sinckler won the most recent of his 68 England caps at the Rugby World Cup in France last autumn.
Ludlam, 28, also played in the tournament, winning his 25th cap in the third-place play off against Argentina.
But both missed out on selection for Borthwick’s squad for this year’s Six Nations.
Former England great Jonny Wilkinson won the second of back-to-back European crowns with Toulon a decade ago.
Bristol director of rugby Pat Lam said of Sinckler: “He has dealt with his fair share of setbacks along the way, and I believe he is playing his best rugby which is a testament to his resilience and determination.
“Like everyone’s journey, there will always be a time it comes to an end and I know Kyle is desperate to finish his time at the Bears on a high and continue his impressive form until the end of the season.”
