The Naval Reserve Officers Training Corps (NROTC) program is a college-based, commissioned officer training program of the United States Navy and the United States Marine Corps.

In 1926, the U.S. Department of the Navy established the Naval Reserve Officer Training Corps. Its purpose was to produce a reserve of qualified officers who would be needed for a possible rapid expansion of the military in the case of an unforeseen emergency. The original units were at the University of California, Northwestern University, University of Washington, Harvard University, Yale University, and Georgia Institute of Technology.

Under the modern U.S. Naval ROTC system, graduates become active duty officers, rather than reserve officers, and are required to serve a term of 5 years for the Navy Option and 4 years for the Marine and Nurse Options. The Naval Reserve Officer Training Corps commissions individuals into either the United States Navy as an Ensign or the United States Marine Corps as a Second Lieutenant. While attending college, these prospective officer candidates are known as Midshipmen. Whereas Naval Academy Midshipmen are on active duty, NROTC Midshipmen are in the Navy Reserve but are on active duty for periods of training during the summer. The primary difference is that NROTC Midshipmen attend an ordinary civilian college or university, whereas Naval Academy Midshipmen attend the U.S. Naval Academy in Annapolis, MD, which is a much more regimented, military environment.

The Reserve Officers' Training Corps (ROTC) is a college-based program for training commissioned officers of the United States armed forces. ROTC officers serve in all branches of the U.S. armed forces. ROTC graduates constitute 56 percent of U.S. Army officers, 11 percent of U.S. Marine Corps officers, 20 percent of U.S. Navy officers, and 41 percent of U.S. Air Force officers, for a combined 39 percent of all active duty officers in the Department of Defense.

Under ROTC, a student may receive a competitive, merit-based scholarship, covering all or part of college tuition, in return for an obligation of active military service after graduation. The U.S. Coast Guard offers a similar program to ROTC under a different name: CSPI (College Student Pre-commissioning Initiative).

The student attends college like other students, but also receives basic military training and officer training for his chosen branch of service, through the ROTC unit at the college or university. The student participates in regular drills during the school year, and extended training activities during the summer.

The Officer Training Corps (OTC) is a part of the British Army which provides military leadership training to students at UK universities. The name Officer Training Corps is misleading in that its mission is not the training of commissioned officers; only a small minority of OTC members go on to further train, and subsequently, commission as officers in the Regular or Territorial Army. However, in recent years there has been a greater effort at OTCs to raise awareness of the career opportunities within the Regular or Territorial Army (although the mission statement (see below) has not changed). It is similar in some ways to the United States Army Reserve Officers' Training Corps with which Cambridge OTC has a regular exchange. However, a fundamental difference in that ROTCs are actually Officer Training Establishments and thus have a rather different ethos and work ethic. The UK Ministry of Defence marketed the OTC as "a University/ College club with a great and varied social life ... where you'll find some of the cheapest drink on campus."

A Naval Reserve is the reserve body of a nation's Navy, typically called-upon in times of conflict. Naval Reserves include: