Kelley Blue Book, headquartered in Irvine, California, is the United States' largest automotive vehicle valuation company. The company's website is a source for new and used vehicle pricing and information. The company has become so identified with its services that the trademarked terms blue book and blue book value have become a genericized trademark with a car's market value.

Kelley Blue Book Co., Inc., began as the Kelley Kar Company, a Los Angeles-based car dealership, in 1918. The dealership was founded by Les Kelley, an Arkansas-born businessman who started the dealership with three used Model T Fords and one employee, his 13-year-old brother Buster.

In order to obtain inventory, he began circulating lists of cars he wanted to acquire along with the price he was willing to pay for them. The price lists quickly became a trusted standard among Los Angeles area banks and car dealers.

In 1926, he published his first Kelley Blue Book, a guide to used car values. The service was primarily regional until the 1940s. In the years immediately following World War II, a large number of returning serviceman and the pent-up demand caused by four years of wartime rationing caused a huge spike in the demand for cars. Since most car companies had yet to retool from wartime production, the price of used cars skyrocketed. During this time, Kelley Blue Book expanded to become a nationwide automobile appraisal guide. The book remained with the Kelley family until 1980.