Officer candidate is a rank in some militaries of the world that is an appointed position while a person is in training to become an officer. More often than not, an officer candidate was a civilian who applied to join the military directly as an officer. Officer candidates are, therefore, not considered of the same status as enlisted personnel.
In some[which?] NATO countries, the term "officer designate"[dubious ] is used. In the NATO rank scale, it comes below the grade of OF-1 and is annotated as OF(D). Ranks designated as OF(D) include dokimos efedros axiomatikos in the Hellenic Army, and chuẩn úy ("officer designate") in the Vietnam People's Army.
In the Finnish Defence Forces, officer candidate is an NCO rank, comparable to sergeant. Usually officer candidates are chosen as conscripts, and along with officer cadets are promoted to the rank of second lieutenant.
The Philippines 
In the Philippines, an officer candidate or OC is a civilian or enlisted personnel who holds a baccalaureate degree and who wants to earn a commission as an officer in the Armed Forces of the Philippines. Upon admission to the Officer Candidate School, officer candidates are appointed as probationary second lieutenants and probationary ensigns.
United Kingdom 
|Commissioned officer ranks of the British Armed Forces|
|NATO rank code||Student Officer||OF-1||OF-2||OF-3||OF-4||OF-5||OF-6
|Royal Navy||O Cdt||Mid||SLt||Lt||Lt Cdr||Cdr||Capt||Cdre||RAdm
|Adm of the Fleet|
|Royal Marines||2Lt||Lt||Capt||Maj||Lt Col||Col||Brig||Maj-Gen||Lt-Gen||Gen
|Army||O Cdt||2Lt||Lt||Capt||Maj||Lt Col||Col||Brig||Maj-Gen||Lt-Gen||Gen
|Royal Air Force||OC / SO||APO / Plt Off||Fg Off||Flt Lt||Sqn Ldr||Wg Cdr||Gp Capt||Air Cdre||AVM||Air Mshl||Air Chf Mshl
United States of America 
Officer candidate 
U.S. Army 
In the United States Army, officer candidates attend either the Federal Officer Candidate School (OCS) at Fort Benning, Georgia, or state National Guard sponsored military academies (Regional Training Institutes) that follow the same curriculum and requirements. Soldiers who attend OCS are usually prior service enlisted personnel, though civilians with college degrees can enlist and go directly to OCS after basic training.
With regard to rank, a U.S. Army officer candidate exists in a gray area. They are enlisted soldiers who lose all rank status when reporting to the course. Regardless of pay grade, candidates are outranked by any course cadre or permanent party enlisted soldiers they may encounter. Although their status does not correspond to a position of authority within the standard U.S. Army ranks, candidates serve in leadership training roles at the platoon or company level. They are addressed as "candidate" by the OCS cadre. During the first few weeks of indoctrination, candidates are treated much the same as a new recruit. In the final weeks of training, OCS platoons may achieve "senior" status and senior officer candidates may be addressed as "Sir" or "Ma'am" by more junior candidates, but never by other enlisted ranks.
The pay grade for a U.S. Army officer candidate is E-5 (Federal OCS), or E-6 (state OCS) on the enlisted pay scale, unless the candidate previously achieved a higher enlisted rank. For example, an E-7 who becomes a candidate would continue to receive E-7 pay. The OCS uniform is stripped of the rank patch which is replaced by the letters "OCS." Upon commissioning, a candidate becomes a second lieutenant.
U.S. Marine Corps 
In the United States Navy, officer candidates are trained at either the Officer Candidate School or Officer Development School in Newport, Rhode Island. A parallel program known as Aviation Officer Candidate School (AOCS) at NAS Pensacola, Florida, previously produced officers slated to become naval aviators, naval flight officers, air intelligence officers and aircraft maintenance duty officers not otherwise procured via the U.S. Naval Academy or NROTC. A major distinction between the two programs was the use of enlisted Marine Corps drill instructors in the AOCS program, a vestige from the World War II and early 1950s period when AOCS graduates were given the option of being commissioned in the U.S. Navy or U.S. Marine Corps before proceeding to flight training. AOCS was disestablished in 1994 due to BRAC action and merged into the current OCS program in 1994.
Officer candidate is also the rank to which participants in the active duty commissioning program "Seaman to Admiral 21" are appointed. STA 21 officer candidates are appointed to the rank at the Naval Science Institute and go on to hold the rank while training with the Naval Reserve Officer Training Corps at NROTC-affiliated universities. While attached to their colleges or universities, officer candidates are looked to as mentors to the midshipmen throughout the school year. They must maintain 2.0 GPAs, perform 25 hours of community service and are urged to take leadership positions within their unit.
STA 21 OCs maintain their enlisted pay grade and eligibility for enlisted advancement. The number of sailors selected each year to participate in the "Seaman to Admiral 21 program" varies from year to year. Fiscal year 2010 admitted about 200 candidates, FY11- 115, and FY12- about 75.
The rank of officer candidate is denoted by an officer's uniform with no insignia except for a line officer's star device on white and dress blue uniforms. On khaki and working blue uniforms, fouled anchors are worn on the collar points until candidate officer status is achieved, at which time OCs wear the bar insignia similar to their senior/midshipmen 1st class counterparts at the U.S. Naval Academy and in NROTC.
U.S. Coast Guard 
Officer trainee 
U.S. Air Force 
Similar to the Army officer candidates, Air Force officer trainees exist in a gray zone with regard to rank, and their status does not directly correspond to a position of seniority or authority within the standard Air Force ranks. Typically, they are referred to or addressed as "OT," and during the first few weeks of indoctrination, are treated much the same as a new recruit. The pay for an officer trainee, however, is equal to an E-5 on the enlisted pay scale, unless the candidate previously achieved a higher enlisted rank than E-5, e.g., an E-7 who becomes a candidate would continue to receive E-7 pay, and so on. Once commissioned, the new officer advances to the pay rate of O-1, unless they have at least four years of active duty service, in which case they are paid the higher O-1E rate in recognition of the prior enlisted service. Such pay continues at promotion to the next two grades ("O-2E" and "O-3E"), but is discontinued at the grade of O-4.
OT rank insignia loosely parallels that of Air Force ROTC and United States Air Force Academy Cadet Insignia, except in the case of the directly commissioned chaplains, lawyers, and medical personnel.
|United States commissioned officer and officer candidate ranks|
|Pay grade / Branch of service||Officer
|Approximate insignia||(no universal insignia)||(no universal insignia)|
|Air Force||Cadet / OT||2d Lt||1st Lt||Capt||Maj||Lt Col||Col||Brig Gen||Maj Gen||Lt Gen||Gen||GAF|||
|Army||CDT / OC||2LT||1LT||CPT||MAJ||LTC||COL||BG||MG||LTG||GEN||GA||GAS|
|Marine Corps||Midn / Cand||2ndLt||1stLt||Capt||Maj||LtCol||Col||BGen||MajGen||LtGen||Gen|||||
|Navy||MIDN / OC||ENS||LTJG||LT||LCDR||CDR||CAPT||RDML||RADM||VADM||ADM||FADM||AN|
|Coast Guard||CDT / OC||ENS||LTJG||LT||LCDR||CDR||CAPT||RDML||RADM||VADM||ADM|||||
|Public Health Service||||ENS||LTJG||LT||LCDR||CDR||CAPT||RADM||RADM||VADM||ADM|||||
|National Oceanic and
 Grade is authorized by the U.S. Code for use but has not been created
 Grade has never been created or authorized
|United States warrant officer ranks|
|Public Health Service|||||||||||
|National Oceanic and
 Grade is authorized for use by U.S. Code but has not been created
 Grade never created or authorized
- "NATO official document". Retrieved 7 September 2010.
- Army.com - Officer Candidate School
- Army Regulation 350-51 United States Army Officer Candidate School. June 11, 2001. Chapter 5-2. Retrieved February 9, 2011.