Mastitis is one of the most common diseases in cattle. The causes are complex, and the disease tends to recur and its difficult to cure, resulting in significant economic losses to the global dairy industry each year. Circular RNAs (circRNAs), a class of endogenous non-coding RNAs (ncRNAs), have recently been recognized as key regulators in inflammatory diseases. However, little is known about the roles of circRNAs in mastitis caused by Staphylococcus aureus (S. aureus) infection. In this study, bovine mammary gland tissue was treated with S. aureus (10