The fast food giant is seeking compensation of 1.5 million yuan ($242,000) and an apology.
One of the posts said chickens used by KFC were genetically modified to have six wings and eight legs.
A case has now been filed before a court in Shanghai.
KFC says the rumors appeared in posts on the WeChat app.
The company said in a statement that the rumors had spread through at least 4,000 subsequent posts.
KFC China’s president Qu Cuirong said: “This not only seriously misled consumers, but also hurt our brand.”
The fast food giant named the original posters as Shanxi Weilukuang Technology Company Ltd, Taiyuan Zero Point Technology Company and Yingchenanzhi Success and Culture Communication Ltd.
The companies have not commented on the court complaint.
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