The 37-year-old is suing Marketing Advantages International and its jewellery website Emitations.Com over advertisements that included her image, reported TMZ Online.
The lawsuit claimed the company used her name and face to sell jewellery, including an imitation of her engagement ring.
Witherspoon claimed she never gave permission to the company to use her to sell its good and is suing for unspecified damages.
An image of the 'Sweet Home Alabama' star can be seen on the Emitations.Com website with her face resting on her right hand with a ring purported to be her engagement ring on.