The United States Navy Reserve (USNR), known as the United States Naval Reserve from 1915 to 2004, is the Reserve Component (RC) of the United States Navy. Members of the Navy Reserve, called reservists, are categorized as being in either the Selected Reserve (SELRES), the Training and Administration of the Reserve (TAR), the Individual Ready Reserve (IRR), or the Retired Reserve.

The mission of the Navy Reserve is to provide strategic depth and deliver operational capabilities to the Navy and Marine Corps team, and to the Joint forces, in the full range of military operations from peace to war.

The Navy Reserve consists of 56,254 officers and enlisted personnel who serve in every state and territory as well as overseas as of June 2023.

The largest cohort, the Selected Reserve (SELRES), have traditionally drilled one weekend a month and performed two weeks of active duty annual training during the year, receiving base pay and certain special pays (e.g., flight pay, dive pay) when performing Inactive Duty Training (IDT, aka "drills"), and full pay and allowances while on active duty for Annual Training (AT), Active Duty for Training (ADT), Active Duty for Operational Support (ADOS), Active Duty for Special Work (ADSW), under Presidential Selected Reserve Call-up (PSRC) / Mobilization (MOB) orders, or when otherwise recalled to full active duty.

Every state, as well as Guam and Puerto Rico, has at least one Navy Reserve Center (NRC, formerly known Naval Reserve Centers (NAVRESCEN) until 2005 and formerly known as Navy Operational Support Centers (NOSC) from 2005 to 2021), staffed by full-time active duty Training and Administration of the Reserve (TAR) personnel, where SELRES officers and sailors typically come to do their weekend drills. The size of these centers varies greatly, depending on the number of assigned SELRES. Some NRCs may be collocated with Marine Corps Reserve Centers (MARESCEN) and were often known as Naval and Marine Corps Reserve Centers (NAVMARCORESCEN) prior to 2005. Other NRCs may be part of or tenant commands at Armed Forces Reserve Centers or Joint Reserve Centers with Army Reserve, Marine Corps Reserve, and/or Army National Guard units.

Navy Reserve Centers are intended mostly to handle administrative functions and classroom style training. However, some NRCs have more extensive training facilities, including SECRET or SCIF level intelligence centers, damage control trainers and small boat units. Some NRCs are co-located on existing military facilities, but many are "outside-the-wire" standalone facilities that are often the only U.S. Navy representation in their communities or even the entire state, commonwealth or territory. Because of this, NRCs outside of the Navy's Fleet traditional Concentration Areas (e.g., Norfolk, VA; San Diego, CA; Jacksonville, FL, Honolulu, HI, etc.) are also heavily tasked to provide personnel, both TAR staff and SELRES, for participation in Funeral Honors Details. This service provided to the local community is one of the NRC's top two priority missions (the other being training and mobilization of SELRES).

Many SELRES are assigned to front-line operational units outside of the NRC structure, many of them combat-coded, such as Naval aviators, Naval Flight Officers, Naval Flight Surgeons, enlisted Naval Aircrewmen, and other officer and enlisted personnel assigned to Navy Reserve or Active-Reserve Integrated (ARI) aviation squadrons, air groups and air wings, or personnel assigned to major unified combatant command, Fleet and other major staff positions. These personnel, especially active flight crew, are typically funded for far more duty than the notional one weekend per month/two weeks per year construct typically associated with the Reserve and often perform military duty well in excess of 100-man-days per year. SELRES have also performed additional duty in times of war or national crisis, often being recalled to full-time active duty for one, two or three or more years and deploying to overseas locations or aboard warships, to include active combat zones, as seen during Operations Enduring Freedom and Iraqi Freedom.

TAR (Training and Administration of the Reserve) personnel are Navy Reserve personnel who serve in uniform year round and provide administrative support to Navy Reserve SELRES and IRR (to include VTU) personnel, active duty Navy personnel in areas where there are no major naval installations (i.e., Navy Recruiting Command personnel and NROTC staff at civilian colleges and universities), retired military personnel and family members of all the U.S. military services, and operational support for the Navy.