CarMax is the United States' largest used-car retailer and a Fortune 500 company. The first CarMax location opened in September 1993. As of March 2017, the company had 173 locations. Prior to the first store being built, DeVito/Verdi was hired as the advertising agency and creative resource. The company executed the campaign and additional TV advertisements over the course of a number of years in support of the launch and the initial wave of stores.

CarMax doesn't sell used cars exclusively. They also sell new Toyota vehicles at their Kenosha, Wisconsin and Laurel, Maryland locations.

The concept for CarMax was developed by Circuit City executives under then-CEO Richard L. Sharp. It was developed for nearly a year in 1991, using the code name "Project X", and was also known as "Honest Rick's Used Cars" to those intimately involved in the skunk works team. The concept was actually first proposed by a consultant hired by Circuit City to evaluate possible business opportunities beyond the scope of their consumer electronics locations. While used cars have always been the main business, CarMax purchased the rights to locations from car manufacturers such as Chrysler, Mitsubishi, and Toyota. CarMax also purchased an auto row in Kenosha, Wisconsin that had additional manufacturer franchises, such as Ford, BMW, and Volvo. The first CarMax location opened in September 1993, 1.7 miles (2.7 km) from Circuit City's corporate offices in Richmond, Virginia. As of November 30, 2016, CarMax operated 169 locations across 39 states.

The business model began with no fees, however the model was subsequently abandoned for the current business model after it was determined that customers were not concerned about paying transaction fees for the purchase of a vehicle.

A typical CarMax store is approximately 59,000 square feet (5,500 m), carries an inventory of 300–400 vehicles, and turns its inventory over eight to ten times a year. On average, a CarMax location employs 40 sales associates. Each car goes through a thorough 125-point inspection process, beyond any state-required inspections, and includes a 30-day warranty and a five-day money back guarantee.

Circuit City issued the first CarMax stock in February 1997, when CarMax had seven locations. Initially, the stock was a tracking stock still under the umbrella of the Circuit City. CarMax officially split from Circuit City as of October 1, 2002, when it was spun off as a stock dividend for Circuit City shareholders, with shares also issued to those holding CarMax tracking stock.

During the 12-month period ending February 28, 2015, the company sold 582,282 used cars. According to the CarMax fiscal year 2009 report released on April 2, 2009, the company opened 11 used car superstores, including superstores in 5 new markets.

CarMax was on Fortune's "100 Best Companies to Work For" list from 2005 to 2016, placing 85th in 2016.