Four U.S. Marines and a United States Navy Sailor are killed in the a shooting spree targeting military installations in Chattanooga, Tennessee.

The United States Marine Corps (USMC), also referred to as the United States Marines or simply the Marines, is the maritime land force service branch of the United States Department of Defense. It is responsible for conducting expeditionary and amphibious operations through combined arms, implementing its own infantry, artillery, aerial, and special operations forces. The U.S. Marine Corps is one of the six armed forces of the United States and one of the eight uniformed services of the United States.

The United States Navy (USN) is the maritime service branch of the United States Department of Defense. It is the world's most powerful navy with the largest displacement, at 4.5 million tons in 2021. It has the world's largest aircraft carrier fleet, with eleven in service, one undergoing trials, two new carriers under construction, and six other carriers planned as of 2024. With 336,978 personnel on active duty and 101,583 in the Ready Reserve, the U.S. Navy is the third largest of the United States military service branches in terms of personnel. It has 299 deployable combat vessels and about 4,012 operational aircraft as of 18 July 2023. The U.S. Navy is one of six armed forces of the United States and one of eight uniformed services of the United States.

On July 16, 2015, Muhammad Youssef Abdulazeez opened fire on two military installations in Chattanooga, Tennessee, United States. He first committed a drive-by shooting at a recruiting center, then traveled to a U.S. Navy Reserve center and continued firing, where he was killed by police in a gunfight. Four Marines died on the spot. A Navy sailor, a Marine recruiter, and a police officer were wounded; the sailor died from his injuries two days later.

Chattanooga is a city in Hamilton County, Tennessee, United States, and its county seat. It is located along the Tennessee River and borders Georgia to the south. With a population of 181,099 in 2020, it is Tennessee's fourth-most populous city and one of the two principal cities of East Tennessee, along with Knoxville. It anchors the Chattanooga metropolitan area, Tennessee's fourth-largest metropolitan statistical area, as well as a larger three-state area that includes southeastern Tennessee, northwestern Georgia, and northeastern Alabama.