The Red Bull Racing driver has signed a multi-year contract with Porsche and will compete in Porsche's new LMP1 sports prototype at the Le Mans 24 Hours and in the sports car World Endurance Championship WEC in 2014.
The 36-year-old Australian has raced at Le Mans twice before. In 1998 he finished runner-up in the FIA GT Championship at the wheel of a sports prototype.
In a career in F1 that stretches back to 2002, Webber has won nine grand prix and has started from pole position 11 times.
"It's an honour for me to join Porsche at its return to the top category in Le Mans and in the sports car World Endurance Championship and be part of the team," Webber said in a statement put out by Porsche.
Red Bull boss Christian Horner said earlier this week that Lotus's Kimi Raikkonen could replace Webber as Sebastian Vettel's teammate if the Australian made a decision not to continue with the team.
Fellow Australia Daniel Ricciardo and Jean-Eric Vergne of Toro Rosso remain other possible options to take the second driving spot at Red Bull.