BYD Auto Co., Ltd. is a Chinese automobile manufacturer based in Xi'an, Shaanxi Province, and a wholly owned subsidiary of BYD Company. It was founded in January 2003, following BYD Company's acquisition of Tsinchuan Automobile Company in 2002. Its principal activity is the design, development, manufacture and distribution of automobiles, buses, electric bicycles, forklifts, rechargeable batteries and trucks sold under the BYD brand. BYD has achieved top rankings of J.D Power's Quality Study. BYD has been awarded The Top Crash Facility Award of the year 2013. It also has a 50:50 joint venture with Daimler AG, Shenzhen BYD Daimler New Technology Co., Ltd., which develops and manufactures luxury electric cars sold under the Denza brand. BYD Auto sold a total of 506,189 passenger cars in China in 2013, making it the tenth-largest selling brand and the largest selling Chinese brand. In 2015, BYD Auto was the best selling global electric vehicle brand. For a second year running, BYD was the world's top selling plug-in electric car manufacturer with over 100,000 units delivered in 2016. In October 2016, BYD Auto became the all-time second largest global plug-in car manufacturer. 

In December 2015, Swail passed the BYD Purchasing Supplier Qualification Certification System.