Castex will join Wasps having spent his entire rugby career in France with clubs including Bourgoin, Castres and Dax.
The versatile prop, who can play both tight-head and loose-head, came through the ranks at Bourgoin before joining Castres where he was mentored by All Black prop Carl Hoeft.
During a stint at Dax, Castex suffered an injury which kept him out of the game for a short period so he turned to Narbonne in 2009 to get some vital game time back under his belt. He has played almost every game for the club this season, featuring in every position in the front row.
Known for his technical scrummaging ability, Castex has also developed into an excellent ball carrier in recent years and brings with him a wealth of top flight experience, having played in both the Heineken Cup and Top 14.
London Wasps Chief Executive Chris Thomas said: "We are making no secret of the fact that we want to strengthen our pack in time for next season and this is the first of a number of signings we hope to make in this area. Jeremy's versatility in the front row will be a real asset to the squad."
Jeremy Castex said: "I am really excited to be joining such a fantastic club. It will be a great challenge and I am looking forward to working with some great forwards like Simon Shaw, Joe Worsley and others and being coached by a World Cup winning prop in Trevor Woodman."
Castex is the fourth player to be signed by the club in recent weeks following announcements that backs Nicky Robinson (from Gloucester), Ryan Davis (from Exeter) and Chris Bell (from Sale) will also join London Wasps next season.
*Jeremy Castex will host a live chat this evening at 18.00 (UK time) on his website www.jeremy-castex.rugbyunit.com. He will be assisted by a professional translator and Wasps fans are invited to tune in and ask him their questions.