Karthikeyan is the first Asian driver to be announced as a competitor in the championship, and promises to be a big hit with Speedcar Series fans when he brings his flat-out style to the competition, which starts later this year.
The 30-year-old is a single-seater veteran, having raced across the world in Formula Three, Formula Nippon, and the Dallara Nissan World Series, as well as Formula One, but can't wait to try stock car racing, he said: "I am very much looking forward to being a part of the new Speedcar Series, it is obviously very competitive, with great names such as Jean Alesi and Johnny Herbert, and it will be very exciting to pit myself against these legends of Formula One.
"The winter series is perfect for me as I can concentrate on Formula One, my main obligation, but also be a part of a really serious racing series that keeps me competitive and racing, my only ambition," he added.
His best Formula One result to date was fourth at the 2005 United States Grand Prix.
A host of drivers, including Jean Alesi, Johnny Herbert, Stefan Johansson, and Gianni Morbidelli, were on hand to test three of the new Speedcar Series cars at the Virginia International Raceway, earlier this month.
The first season begins this coming November, and will run until next April.
The series will be officially presented in Dubai later this year.