The 2015 Quaker State 400 was a NASCAR Sprint Cup Series race held on July 11, 2015, at Kentucky Speedway in Sparta, Kentucky. Contested over 267 laps on the 1.5-mile (2.4-kilometre) speedway, it was the 18th race of the 2015 NASCAR Sprint Cup Series season. Kyle Busch won the race, his second of the season. Joey Logano finished second. Denny Hamlin finished third. Carl Edwards and Matt Kenseth rounded out the top five.

With qualifying canceled for bad weather, Kyle Larson was awarded the first starting spot. He failed to lead a single lap and finished a disappointing 35th after cutting down a tire and crashing out late in the race. Busch led a race high of 163 laps on his way to winning the race. The race had 13 lead changes among eight different drivers, as well as a new track record of eleven caution flag periods for 49 laps.

This was the 31st career victory for Kyle Busch, second at Kentucky Speedway, and third at the track for Joe Gibbs Racing. This win moved Busch up to 35th in the points, 87 points behind Cole Whitt for the 30th place Chase for the Sprint Cup cutoff, and 492 behind points leader Kevin Harvick. Despite being the winning manufacturer, Toyota left Kentucky trailing Chevrolet by 83 points in the manufacturer standings.

The Quaker State 400 was carried by NBC Sports on the cable/satellite NBCSN station for the American television audience. The radio broadcast for the race was carried by the Performance Racing Network and Sirius XM NASCAR Radio.

Kentucky Speedway is a 1.5-mile (2.4-kilometre) tri-oval speedway in Sparta, Kentucky.

Kevin Harvick entered Kentucky with a 63-point lead over Dale Earnhardt Jr. Jimmie Johnson entered 67 back, Joey Logano entered 75 back, and Martin Truex Jr. entered 87 back.

On June 16, NASCAR announced that a new aero package would be used for this weekend's race at Kentucky Speedway. The changes included a smaller rear spoiler and other adjustments that significantly reduced aerodynamic downforce. The spoiler was 3.5 inches (8.9 centimetres) tall. There was also a 25-inch (64-centimetre) wide splitter extension. In addition, tires supplied by Goodyear provided drivers with more grip. "We want to see more lead changes on the racetrack," NASCAR Executive Vice-president and Chief Racing Development Officer Steve O'Donnell said in a media teleconference. "We'll evaluate that and a number of different factors coming out of Kentucky, see what we can learn and implement down the road." Originally, the package was to be used at this year's All-Star Race, but the plan was scrubbed and NASCAR opted to use the package for a points race. "Let me be clear. This is not a test, this is a race," O'Donnell said of the rules package that was in effect for the 18th round of the 2015 Sprint Cup Series. "We've had an extensive testing plan with the industry over the last 18 months. We wouldn't implement this if we didn't feel confident as an industry to implement it at Kentucky."

For this weekend's race, teams were given nine sets of Goodyear tires versus the normal allotment of eleven.