The Springbok flyer, who faced the Lions twice in 2009, scoring a crucial try in the second Test, had a year remaining on his contract with the Stormers and Western Province.
But he has been released from the deal early to join the star-studded Top 14 outfit, home to former Lions Gethin Jenkins, Simon Shaw, Andrew Sheridan and Jonny Wilkinson.
Habana hopes to continue playing in the Green and Gold of South Africa but admits the chance to join Toulon was too big to turn down.
"Playing for the Boks is a huge part of my life and I would never turn my back on my country," said Habana.
"I'll never stop giving 100% on the field for any team I play for and if the Springbok coach picks me, I'll be there.
"I've had three great seasons in the Cape thus far and I am looking forward to finishing off on a high before taking on a new challenge overseas.
"It's a wrench to leave my home, even if only for a short while, but the chance to test myself against different opposition in a new environment was difficult to turn down.
"Rugby Club Toulonnais has an incredible pedigree and some phenomenal players and working with everyone there is going to help me improve my game - and hopefully I can bring something new to the team there as well."
Habana is currently recovering from a knee injury but he hopes to finish his Stormers career with a bang.
The rehabilitation has gone well and I haven't experienced any complications at all," added the former IRB Player of the Year.
"We're back at pre-season training now and I'm looking forward to putting in some serious work to get myself back up to speed ahead of the new season.
"I'm 100% focused on what I want to achieve on the field this year and can't wait to get started."