Webb, last season’s Welsh player of the year, was injured during the 23-19 World Cup warm-up victory over Italy in Cardiff on Saturday.
“Wales scrum-half Rhys Webb has sustained a significant midfoot injury ruling him out of the forthcoming Rugby World Cup. Rhys will undergo further examination and assessments on both his foot and knee before further details can be announced,” the Wales Rugby Union said in a press release.
The news comes just a day after full-back Leigh Halfpenny was also ruled out of the World Cup after sustaining knee ligament damage in the same game against the Italians.
Wales head coach Warren Gatland has called Mike Phillips and Eli Walker into his World Cup squad to cover for the two injuries.
Scrum-half Phillips has won 94 caps for Wales and was a surprise omission when Gatland named his 31-man tournament squad, while Ospreys wing Walker made his international debut against Ireland last month.
“It is extremely disappointing for both Leigh and Rhys,” Gatland said.
“They have worked exceptionally hard to establish themselves on the world stage and to prepare for the tournament and we wish them all the best with their recovery.
“After announcing the squad we spoke about the need for players to remain ready for action and it is a great opportunity for Mike and Eli.
“It’s great that we can call on players of this calibre. To bring Mike’s experience into the squad is a bonus along with Eli’s exciting talent.”
Wales are in the toughest-looking group in the first round up against hosts England, former winners Australia, Fiji and Uruguay. – Agence France-Presse