The "Russian Roulette" singer allegedly owes Cindy Percival $26,144.14 in unpaid wages from 2009, says a claim filed at Los Angeles County Superior Court by the fitness expert last week.
In the law suit, Cindy claims she was hired by the singer to perform "exclusive personal training services" at a rate of $1,500-a-day but wasn't paid for a few weeks work between September and October.
In addition, the trainer is also seeking $2,644.14 in travel expenses to cover the costs of her travel around Europe to work with the 22-year-old star.
Rihanna has previously spoken about her exercise regime, admitting she always needs a trainer to motivate her in her work-out sessions.
She said: "I stay in shape with a lot of hard work and a lot of running on the treadmill. Cardio is the key. I have a personal trainer who travels with me if we have a big event coming up."
"I work out every day but I need a trainer to motivate me - I don't find it much fun working out on my own."
