Bridgend born Webb is a product of the Ospreys development pathway and made his senior debut in a 32-7 win over Ulster at the Liberty Stadium in 2008.
Webb made his senior international debut for Wales against Italy during last season's Six Nations and added a further two caps against the Barbarians and Australia last June.
"I'm absolutely thrilled. To be able to commit to another three years with my home region is fantastic," he said.
"It's a brilliant environment here, the only place I want to play rugby.
"Having done so well last season I've obviously been disappointed to not get so much game time this year but I've had to knuckle down and work hard. Kahn has been a great help for me in terms of development and I believe if I keep on working hard I can become a much better player over the three years of my new contract.
"I take great pride in wearing the Ospreys shirt. We've got a good, young group of players together here that can serve the region well for a long time and I'm pleased that I can be a part of it."
Webb joins the likes of Joe Bearman, James King and Lloyd Peers in signing new deals with the Ospreys.