The surprise deal will see the German make his first F1 start aged 32, more than a decade after he was test driver for the Jaguar squad.
He has since established himself as one of the world's best sportscar racers at the factory Audi squad, as well as enjoying single-seater success in Japan's Super Formula (previously Formula Nippon).
“I am delighted to be given the opportunity to take part in a Formula One race weekend – I want to thank Caterham F1 Team for this chance. I’m ready for this challenge and I cannot wait to jump in the car and make the most out of the weekend ahead," said Lotterer.
“I will need to get settled and used to the car quickly, as the team has worked on a number of updates and we will need to have as much time as possible out on track to optimise the car’s performance.
“I really enjoy racing at the legendary circuit of Spa-Francorchamps, it’s one of my favourite tracks and it’s very close to where I grew up, so this makes the weekend even more special and one to remember.”
Lotterer is not believed to be bringing money for the drive. He has extensive experience at Spa-Francorchamps and has already raced there twice this season; as such, he is ostensibly being brought in for his feedback.
However Lotterer also has connections with Colin Kolles, who brokered Caterham's recent ownership change. The German drove for Kolles' sportscar team in 2009, producing a star performance at Le Mans that landed him a factory Audi drive for 2010.
Lotterer has since won the 24 Hours three times, including this year's race, and was FIA World Endurance Champion in 2012. His successes have all come alongside Benoit Treluyer and Marcel Fassler.
Kobayashi's future is unclear, though a Caterham statement said he "remains part of the team".