Flanker Ben Lewis is a product of the Ospreys Academy

The 21-year-old follows Huw Bennett, Filo Tiatia, Shane Williams and Lee Byrne who have all recently agreed new deals at the Liberty Stadium.

The highly-rated open-side, a graduate from the Ospreys Academy, has made an immediate impression on his first full season with the region.

Ospreys head coach Lyn Jones said: "Ben has made fantastic progress and the new contract is recognition of this."

Lewis is seen as a future Wales international and has already caught the eye of Wales head coach Warren Gatland.

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"Ben's taken the opportunities that have come his way this season and has stood out in a number of games, making a huge impression on some knowledgeable rugby people," Jones added.

"He's got a bright future ahead of him and, thankfully, for the next four years we know that it will be with the Ospreys."

Lewis, who combines his rugby with studying a sports science degree at Swansea University, is seen as a long-term successor to Wales open-side Martyn Williams.

Lewis said: "Working with the likes of Ryan Jones, Marty Holah and Filo Tiatia, some of the best guys in the world in their positions in the back-row, can only help me develop as a player.

"I think there's an element of poacher-turned-gamekeeper in my relationship with them, though.

"I'm not just looking to learn from them but to oust them from the team eventually.

"It's a tough ask but I'm looking forward to the future with the Ospreys."