According to Entertainment Weekly, court papers were filed this week against both Winfrey and her studio Harpo, over claims that she did not own the rights to the self-motivational mantra.
Simone Kelly-Brown and her company Own Your Power Communications have said that they originated the phrase despite Winfrey adopting it as her own.
Winfrey is being accused of trademark infringement over the "brazenly unlawful disregard for the existence and use of [Own Your Power Communications'] trademark".
Simone Kelly-Brown is seeking unknown damages, and has insisted that her brand has been "irreparably harmed" by Winfrey's use of the term.
"Harpo has not been served and we have no information about what allegations are being made," a spokesperson for Harpo said in response.
Earlier this month, Winfrey was named CEO of her cable network OWN and will also serve as the channel's chief creative officer.
It has also been rumoured that the former chatshow host is being lined up as one of the top contenders to host next year's Academy Awards ceremony.