Loeb himself will compete, with the nine-times WRC champion set to pair up with Portuguese driver Alvaro Parente.
It will be the first time the Frenchman Loeb's team will compete in an international GT series.
"The FIA GT Series fits all of our criteria, with 100 per cent professional driving squads and sprint-type races," said team manager Dominique Heintz.
"On one hand, we wanted to take the next step in GT. On the other, Sébastien wanted to make a solid reconversion to circuit racing."
Loeb will race the entire championship, a move away from the odd one-off appearances he has made over the past few seasons.
"I want to prepare to drive in the WTCC project with Citroën and that’s going to happen with a circuit focused schedule in 2013," Loeb said.
"I like sprint races and I appreciate GTs, which are cars that are very nice to drive. I don’t yet know all the ins and outs of circuit racing and I really wanted to drive with another pro to learn and progress. Sharing the wheel with one of the best GT drivers is the ideal solution."
Parente will bring a wealth of experience to the team, despite his tender age of 28.
The Portuguese was British F3 champion in 2005, Formula Renault 3.5 winner in 2007 and boasts two wins in GP2.
"I’m simply very happy," he said. "Two big names are joining together, Sébastien Loeb Racing and McLaren. This package gives me the confidence to have a solid season.
"Everyone knows Sébastien’s talent and he’s shown his ability to adapt quickly to new situations. To be driving with him is incredible.
"I discovered the team during a test at Navarra, with a perfect working environment.
"As always, the target will be to be fast and aim for the highest position. I’m looking forward to drive for Sébastien Loeb Racing and McLaren, with the MP4-12C that I know very well and that I enjoy."
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