Nvidia has said that it faces 51 civil complaints over alleging price fixing and anti-competitive agreements between itself and AMD.
According to Dow Jones, the majority of the lawsuits were filed in the Northern District of California; several were filed in the Central District of California and other cases were filed in several other federal district courts.
Most of the lawsuits are putative class-actions alleging classes of direct or indirect purchasers of Nvidia's graphic processing units and cards.
Nvidia says that the allegations are without merit and that it plans to "vigorously" defend itself.
Last November the US DoJ's antitrust division issued subpoenas against Nvidia and Advanced Micro Devices in an investigation of potential antitrust violations related to graphics processors and cards.