Press Association Sport understands that months of speculation surrounding Halfpenny's future will be formally ended with an announcement by the wealthy French club.
Halfpenny, 25, is understood to have turned down contract offers from both his current team Cardiff Blues and the Welsh Rugby Union.
His existing Blues contract expires at the end of this season, and he is now set to link up with the likes of Jonny Wilkinson, Matt Giteau and Bryan Habana at Stade Felix Mayol.
Halfpenny was last season's Six Nations player of the tournament and British and Irish Lions man of the Test series in Australia.
He also finished as runner-up to Andy Murray in the 2013 BBC Sports Personality of the Year awards, and was named Welsh Sports Personality of the Year.
Halfpenny looks set to join Wales colleagues Jamie Roberts, Dan Lydiate, Mike Phillips and James Hook in the French Top 14, while centre Jonathan Davies (Clermont Auvergne) and lock Ian Evans (Toulon) will also head to France later this year.
Halfpenny has scored almost 350 points in 48 Tests for Wales, and he will be an integral part of their RBS 6 Nations title hat-trick bid this term.
Wales kick off their Six Nations campaign at home to Italy in nine days' time.