The Junior Reserve Officers' Training Corps (JROTC) is a federal program sponsored by the United States Armed Forces in high schools and also in some middle schools across the United States and at US military bases across the world. The program was originally created as part of the National Defense Act of 1916 and later expanded under the 1964 ROTC Vitalization Act.

According to Title 10, Section 2031 of the United States Code, the purpose of the Junior Reserve Officers' Training Corps is "to instill in students in [the United States] secondary educational institutions the values of citizenship, service to the United States, and personal responsibility and a sense of accomplishment." Additional objectives are established by the service departments of the Department of Defense. Under 542.4 of Title 32 (National Defense) of the Code of Federal Regulations, the Department of the Army has declared those objectives for each cadet to be:

Section 524.5 of the CFR National Defense title states in part that JROTC should "provide meaningful leadership instruction of benefit to the student and of value to the Armed Forces. ...Students will acquire: (1) An understanding of the fundamental concept of leadership, military art and science, (2) An introduction to related professional knowledge, and (3) An appreciation of requirements for national security. The dual roles of citizen/soldier and soldier/citizen are studied. ... These programs will enable cadets to better serve their country as leaders, as citizens, and in military service should they enter it. ... The JROTC and NDCC are not, of themselves, officer-producing programs but should create favorable attitudes and impressions toward the Services and toward careers in the Armed Forces." This, importantly, does not mean the cadet has any obligation to join any branch of the Armed Forces as the last sentence stresses.

The military has stated that JROTC will inform young Americans about the opportunities available in the military and "may help motivate young Americans toward military service." A 1999 Army policy memorandum stated that "While not designed to be a specific recruiting tool, there is nothing in existing law that precludes ... facilitating the recruitment of young men and women into the U.S. Army," directing instructors to "actively assist cadets who want to enlist in the military [and] emphasize service in the U.S. Army; facilitate recruiter access to cadets in JROTC program and to the entire student body ... [and] work closely with high school guidance counselors to sell the Army story."

In a February 2000 testimony before the House Armed Services Committee, the armed service chiefs of staff testified that 30%–50% of graduating JROTC cadets go on to join the military:

General Colin Powell said in his 1995 autobiography that "the armed forces might get a youngster more inclined to enlist as a result of Junior ROTC," but added that "Inner-city kids, many from broken homes, found stability and role models in Junior ROTC." U.S. Congress found in the Recruiting, Retention, and Reservist Promotion Act of 2000 that JROTC and similar programs "provide significant benefits for the Armed Forces, including significant public relations benefits." Former United States Secretary of Defense William Cohen referred to JROTC as "one of the best recruitment programs we could have."

Six of the eight branches of the Uniformed services of the United States maintain a Junior Reserve Officers' Training Corps, organized into units. There are a total of 3,275 units:

Prior to 1967 the number of units was limited to 1,200. The cap was increased to 1,600 units in 1967 and again to 3,500 units in 1992; the statutory limitation on the number of units was struck from the law in 2001. Their goal was to reach 3,500 units by February 2011 by encouraging program expansion into educationally and economically deprived areas.