The Welshman was at his most influential in the decisive third Test, kicking 21 points - a new Lions Test record - as well as setting up two tries in the 41-16 victory.
And with his contract with Cardiff Blues expiring at the end of this season, Top 14 giants and reining European champions Toulon pounced to bring Halfpenny to France.
The 25-year-old put pen to paper on an initial two-year deal, with an option of a third year, and has full release for all Wales training camps and international matches.
"I believe the move to Toulon is the best decision for me and my continued development as a rugby player and as a person," said Halfpenny, who will join up with fellow British & Irish Lion Ian Evans in Toulon.
"They are an outstanding club, very ambitious, full of world-class players and are the European champions.
"Toulon are fully supportive of my international desires and duties and I would like to thank them for this as it was an important factor in my decision.
"As well as the rugby challenges, I'm looking forward to experiencing and embracing a new culture and learning a new language. However, until then I'm completely focused on performing for the Cardiff Blues and Wales."