The 28-year-old agrees to a new two-year deal with the One-Day Cup winners after nine seasons at Taunton during which he has taken 240 wickets
Jack Leach has committed to Somerset until 2022 after signing a fresh two-year deal with the Taunton club.
The 28-year-old's deal was due to expire at the end of next season, but he has agreed to fresh terms to remain.
Since making his first-class and List A debut for Somerset in 2012, Leach has taken 240 wickets across both formats.
Those displays have earned him nine Test outings for England, a number which is set to increase during the series against New Zealand which is scheduled to get underway next week.
"I’m very happy to sign this new contract," said Leach, who took 51 Championship wickets last season. "I’m a Somerset fan at heart so I’m very proud to represent the County.
"I have a great relationship with the Members and fans, and I can’t thank them enough for the support they give the team and me as an individual.
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"I’d also like to thank Jason Kerr and Andy Hurry for the belief they have shown in me. I’m looking forward to the winter and can’t wait for next season!"
Director of cricket Andy Hurry added: "Everyone at the Club is delighted that Jack has committed his future to Somerset. He is an exceptional talent and a big influence in the dressing room. I can’t speak highly enough of him both as a player and as a man.
"He has a genuine passion for the game and in particular for Somerset. That shows itself every time he trains, in his diligent preparation and in his wholehearted performances every time he takes to the field. We feel that he has a major role to play for both Somerset and England over the forthcoming years."
Leach becomes the latest high-profile figure to commit his future to Somerset, who finished second in Division One of the County Championship and won the One-Day Cup last season.
Lewis Gregory, George Bartlett, Tom Lammonby, Eddie Byrom, Steve Davies and head coach Jason Kerr have all signed new deals since the conclusion to the campaign.
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