Warships were designated and numbered in system originating in 1895.  Under this system, ships were designated as "Battleship X", "Cruiser X", "Destroyer X", "Torpedo Boat X" and so forth where X was the series hull number as authorized by the US Congress.  These designations were usually abbreviated as "B-1", "C-1", "D-1", "TB-1" and so forth.  This system became cumbersome by 1920, as many new ship types were developed that needed new categories assigned, especially in the Auxiliary ship area.  On 17 July 1920, the system was revised so that all ships were designated with a two letter code, with the first letter being the ship type and the second letter being the sub-type.  Hull numbers were reassigned as necessary.  For example, the Repair ship Prometheus was re-designated as AR-4, with the "A" standing for Auxiliary, the "R" for Repair and the 4 meaning the fourth ship in that series.  Ship types that did not have a subclassification simply repeated the first letter.  So, Battleships became "BB-X" and Destroyers became "DD-X" with X being the same number as previously assigned.

It should be noted that in the United States Navy, unlike European Navies, the first ship in a class to be authorized by the US Congress is the designated class leader (class name ship), regardless of the order in which the ships in that class are laid down, launched or commissioned.  For example, contrary to many European texts, the battleship USS Colorado BB-45 (commissioned 30 August 1923) is the class leader under USN designation standards, not USS Maryland BB-46 (commissioned 21 July 1921).  These battleships are thus properly designated as being "USS Colorado BB-45 Class" and not as "USS Maryland BB-46 Class."

Please note that the listings below include many designations that are no longer used by the current-day US Navy and that others were proposed designations not actually used or were intended for ships that were never built.
 

Aircraft Carriers
 

ACV	Aircraft Carrier, Auxiliary
AVG	Escort Carrier, Auxiliary
AVT	Aircraft Carrier, Training Ship
CV	Aircraft Carrier
CVA	Aircraft Carrier, Attack
CVAN	Aircraft Carrier, Attack, Nuclear Powered
CVB	Aircraft Carrier, Large
CVE	Aircraft Carrier, Escort
CVGH	Aircraft Carrier, Guided Missile Helicopter
CVH	Aircraft Carrier, Helicopter
CVL	Aircraft Carrier, Light
CVN	Aircraft Carrier, Nuclear Powered
CVS	Prior to 1957:  Seaplane Carrier After 1957:  Anti-Submarine/Support Carrier
CVV	Aircraft Carrier, Vertical Take Off And Landing

Notes:

The CVB and CVL designations were established within the original CV designation on 15 July 1943.  The CVS designation was established in 1957. CVA replaced both CV and CVB on 1 October 1952.  CVL went out of use on 15 May 1959 when the last light carrier was decommissioned.  With the decommissioning of the last CVS in 1974, CV and CVN replaced CVA and CVAN on 30 June 1975 as carriers are now considered to be multi-mission capable rather than specialized.

Escort Aircraft Carriers were originally designated AVG (Escort Carrier, Auxiliary) on 31 March 1941, with the USS Long Beach AVG-1 being the first ship so commissioned on 2 June 1941.  This designation was changed on 20 August 1942 to ACV (Aircraft Carrier, Auxiliary), and then changed again on 15 July 1943 to CVE.  Escort Carriers built for the British Royal Navy were designated BAVG until they were transferred.  The CVE designation went out of use when the remaining escort carriers were reclassified AKV (Auxiliary, Aircraft Ferry) on 7 May 1959.

A common question is "what does the 'V' stand for in CV or CVA or CVS or CVE?"

[Thanks to C. Bossie who provided much of the following answer.]

The following is taken from "United States Naval Aviation 1910-1995, Appendix 16:  US Navy and Marine Corps Squadron Designations and Abbreviations":

On 17 July 1920, the Secretary of the Navy prescribed a standard nomenclature for types and classes of NAVAL VESSELs, including aircraft, in which lighter-than air craft were identified by the type "Z" and heavier-than air craft by the letter "V".  The reference also speculates that:  "The use of the "V" designation has been a question since the 1920s.  However, no conclusive evidence has been found to identify why the letter "V" was chosen.  It is generally believed the "V" was in reference to the French word volplane.  As a verb, the word means to glide or soar. As a noun, it described an aeronautical device sustained in the air by lifting devices (wings), as opposed to the bag of gas that the airships (denoted by "Z") used.  The same case may be regarding the use of "Z".  It is generally believed the "Z" was used in deference to Count Ferdinand von Zeppelin.  However, documentation has not been located to verify this assumption."

Battleships
 

B/BB	Battleship
BBC	Battleship, Command Ship
BBG	Battleship, Missile
BBH	Battleship, Helicopter
BM	Monitor

Note:

The "BBC" "BBG" and "BBH" designations were all for proposed conversions of Iowa class (BB-61) battleships, the first two during the 1950s while the last one was during the 1980s commission.  None of these conversions ever took place.
 

Cruisers
 

ACR	Armored Cruiser
C	Cruiser
CA	Prior to 1931:  Armored Cruiser After 1931:  Heavy Cruiser - a cruiser armed with guns 8" (20.3 cm) or larger
CAG	Heavy Cruiser, Guided Missile - a heavy cruiser converted to carry missiles
CB	Large Cruiser
CBC	Large Command Ship
CC	Prior to 1961:  Battlecruiser After 1961:  Command Ship
CF	Flight-deck Cruiser
CG	Guided Missile Cruiser
CGH	Guided Missile Cruiser with an assigned Helicopter
CGN	Guided Missile Cruiser, Nuclear
CH	Cruiser with an assigned Helicopter
CL	Light Cruiser - cruiser armed with guns smaller than 8" (20.3 cm)
CLAA	Anti-Aircraft Light Cruiser
CLC	Command Light Cruiser
CLG	Light Guided Missile Cruiser - a light cruiser converted to carry missiles
CLGN	Light Guided Missile Cruiser, Nuclear
CLH	Helicopter Light Cruiser - cruiser with an assigned Helicopter
CLK	Light Cruiser, Killer (ASW)
CLV	Aviation Cruiser
CS	Scout Cruiser
CSG	Strike Missile Cruiser

Notes:

The history of cruiser classification is somewhat complicated.  Initially, there were three major classifications:  Protected and Peace Cruisers were designated "C-X", Armored Cruisers were designated "ACR-X" and Scout Cruisers were designated "CS-X".  There were also other, non-classified, cruisers which were not assigned hull numbers.  In addition to the initial reclassification of 17 July 1920 mentioned above, there was a second reclassification on 8 August 1921.  Under this final system, the Scout cruisers of the Salem and Omaha classes were merged into a single new category, Light Cruisers, and were given the hull series numbers CL-1 to CL-13.  The older surviving Protected and Peace Cruisers were redesignated as Light Cruisers and assigned hull series numbers CL-14 to CL-23.  The newer Peace Cruisers were reclassified as gunboats (PG-27 to PG-34 and PG-36) while Armored Cruisers were redesignated as "CA-X".  Many cruisers changed categories and hull series numbers.  For example, USS Minneapolis was previously designated as C-13 but was now designated as CA-17.  All previously un-numbered cruisers were classified into one of these categories and received hull series numbers accordingly.  Finally, the new 10,000 ton cruisers built during the 1920s were commissioned into the CL series.

This classification system was used throughout the 1920s.  Then, as a result of the provisions of the London Conference of 1930, cruisers were split into two categories, heavy and light.  The main differentiator was the size of the guns carried, with those cruisers having guns of 8" (20.3 cm) now being designated as "Heavy Cruisers" and cruisers with smaller gun calibers being designated as "Light Cruisers."  On 1 July 1931, this new classification was made official in the USN, and the term "Heavy Cruiser" replaced "Armored Cruiser" as the meaning of the "CA" designation.  Under this new classification system, the cruisers USS Pensacola CL-24 through USS Portland CL-33 were redesignated as CA-24 through CA-33.  Thus, these ships retained their previous Light Cruiser series numbers, even though the last Armored Cruiser, USS Charleston, was CA-19.  From this point on, all heavy and light cruisers built between 1931 and 1949 were commissioned into a single series of hull numbers.

The Lexington class were the only battlecruisers ever laid down by the USN and were assigned hull series numbers CC-1 to CC-6.  When construction was suspended following the Washington Naval Limitation Treaty of 1922, two of these ships, USS Lexington CV-2 and USS Saratoga CV-3, were completed as Aircraft Carriers.  The later Alaska class were designated as Large Cruisers and assigned hull series numbers CB-1 to CB-6.  The USN did not considered these ships to be battlecruisers.

In the late 1940s and 1950s, four new cruiser classification groups were created:

• Anti-aircraft Cruisers - On 18 March 1948 anti-aircraft cruisers of the USS Atlanta CL-51 class were redesignated as CLAA, but retained their previous cruiser series hull numbers.  An improved anti-aircraft cruiser class was cancelled in the 1940s and no other ships were ever given the CLAA classification.
• ASW Cruisers - A planned class of submarine Hunter-Killer Cruisers were designated CLK and numbered in a separate series, but only one ship of this type, USS Norfolk CLK-1, was actually laid down and she was redesignated as Destroyer Leader DL-1 on 2 February 1951 prior to her commissioning on 4 March 1953.
• Missile Cruisers - Two Baltimore class Heavy Cruisers and six Cleveland class Light Cruisers were converted into Guided Missile Cruisers in the late 1950s and early 1960s.  These missile ships kept some of their large-caliber guns and started a new numeric series, but retained their previous sub-type designations as either CAG-X (Heavy Missile Cruiser) or CLG-X (Light Missile Cruiser).  Three other Baltimore and Oregon City class heavy cruisers had all of their former gun armament and superstructures removed and were more heavily modified into all-missile cruisers.  These three cruisers formed a single class (Albany) and were designated as CG-10 to CG-12.  Two, or possibly three, other planned conversions were cancelled and their hull numbers (13 to 15) were not reassigned.  Follow-on missile cruisers built as such from the keel up were commissioned into this same numeric series but were designated as CG-X for conventionally powered ships and CGN-X for nuclear powered ships.  The first of these, the nuclear powered missile cruiser USS Long Beach, was originally designated as CLGN-160 but finally commissioned as CGN-9.  On 1 May 1968 the Guided Missile Heavy Cruisers USS Boston (CAG-1) and USS Canberra (CAG-2) reverted back to their original Heavy Cruiser classifications CA-69 and CA-70, respectively, although they retained their Terrier missile launchers.  On 30 June 1975, a large number of "Frigates" previously designated as DLG-X and DLGN-X were redesignated as Guided Missile cruisers CG-X and CGN-X but retained their original hull numbers.  At the same time, the remaining CLGs that were still active or in reserve were redesignated as CGs.  Finally, the Ticonderoga class DDGs became CGs on 1 January 1980, but retained their original hull numbers.  As a result of this last reclassification, the hull numbers CG-42 to CG-46 were never assigned to any ship.
• Command Cruisers - Command Cruisers (later, Command Ships) had little armament but were equipped as fleet flagships with a great deal of command, control and communications facilities.  USS Northampton (ex-CA-125) was launched as CLC-1 on 27 January 1951 and later redesignated as CC-1 on 15 April 1961.  As noted above, previous to this time CC had been the designation for Battlecruiser.  The light carrier USS Wright (CVL-47) was designated CC-2 on 15 March 1962 and then converted into a Command Ship.  It was planned to convert the Large Cruiser USS Hawaii (CB-3) into a large command cruiser and she was so redesignated as CBC-1 on 26 February 1952 but this conversion was later cancelled and she reverted back to her original designation on 9 October 1954.

Destroyers
 

D/DD	Destroyer
DE	Destroyer Escort
DDE	Destroyer converted to Fleet Escort
DDG	Guided Missile Destroyer
DDH	Destroyer with an assigned Helicopter
DDR	Radar Picket Destroyers
DL	Destroyer Leader or Frigate
DLG	Destroyer Leader or Frigate, Guided Missile
DLGN	Destroyer Leader or Frigate, Guided Missile, Nuclear
TB	Torpedo Boat

.

Frigates/Corvettes
 

F/FF	Frigate.  Originally called ocean escort Name is sometimes used interchangeably with "Destroyer Escort."
FFG	Guided Missile Frigate
FFH	Frigate with an assigned Helicopter
FFT	Reserve/Training Frigate
PE	Patrol Escort
PF	Corvette
PFG	Guided Missile Corvette
PFR	Radar Picket Corvette

.

Submarines
 

APS	Auxiliary Cargo Submarine
NSSN	New Nuclear Attack Submarine (temporary designation)
S/SS	Submarine (Attack/Fleet)
SC	Cruiser Submarine
SF	Fleet Submarine
SM	Submarine, Minelayer
SSA/AGSS	Auxilary/Experimental Submarine
SSB	Submarine, Ballistic Missile
SSBN	Submarine, Ballistic Missile, Nuclear
SSG	Attack Submarine, Guided Missile
SSGN	Attack Submarine, Guided Missile, Nuclear
SSK	Hunter-Killer Submarine
SSM	Midget Submarine
SSN	Attack Submarine, Nuclear
SSP	Transport Submarine
SSR	Radar Picket Submarine
SSRN	Radar Picket Submarine, Nuclear
SST/T	Submarine, Target/Training

.
Note:

Early submarines were given the designation "Submarine Torpedo Boats" (later shortened to just "Submarine") and most were given fish names.  On 17 November 1911 these names were discontinued and in their place was substituted an alphanumeric designation representing their type and size.  For example, USS Pike (S-6) was renamed as USS A-5 (S-6).  This practice of giving submarines an alphanumeric name in addition to their hull series number was continued until 1931.  In that year, submarines built after World War I were given fish names again and most were redesignated into a single hull number series.  New submarines continued to be designated in this numeric series until just recently, when the Seawolf class submarines were designated as SSN-21 to SSN-23, apparently meaning "21st century" submarine.  The follow-on Virginia class submarines will continue the previous series, starting at SSN-774.
 

Amphibious Forces
 

LCAC	Air Cushion Landing Craft
LCC	Amphibious Command Ship
LCI	Infantry Landing Craft
LCM	Mechanized Landing Craft
LCM/ML	Minelaying Mechanized Landing Craft
LCR	Riverine Landing Craft
LCS	Support Landing Craft
LCT	Tank Landing Craft
LCU	Utility Landing Craft
LCV	Vehicle Landing Craft
LCVP	Vehicle and Personnel Landing Craft
LCW	Wing-in-Ground-Effect Landing Craft
LHA	Amphibious Assault Ship
LHD	Amphibious Assault Ship
LKA	Amphibious Cargo Ship
LPD	Amphibious Transport Dock Ship
LPH	Amphibious Assault Helicopter Carrier
LSD	Dock Landing Ship
LSM	Medium Landing Ship
LSS	Landing Support Ship
LSSL	Small Landing Support Ship
LST	Tank Landing Ship
LST/ML	Minelaying Tank Landing Ship
LSU	Utility Landing Ship
LSV	Vehicle Landing Ship

.

Littoral Warfare Ships
 

PAC	Air Cushion Patrol Craft
PB	Patrol Boat
PBL	Amphibious Assault Patrol Boat
PBM	Riverine Monitor
PC	Coastal Patrol Craft/Submarine Chaser (173 ft)
PCC	Submarine Chaser (control)
PCE	Submarine Chaser (Escort)
PCEC	Escort (control)
PCE(R)	Escort (Rescue)
PCI	Fast Coastal Interceptor
PCS	Submarine Chaser (136 ft)
PCSC	Submarine Chaser (control)
PG	Patrol Gunboat
PGM	Missile Gunboat
PGH	Helicopter Gunboat
PH	Hydrofoil Gunboat
PHM	Missile Hydrofoil
PHT	Hydrofoil Torpedo Boat
PL	High Endurance Cutters
PM	Medium Endurance Cutters
PR	Radar Picket Conversion
PSOC	Special Operations Craft
PT	Torpedo Boat
PTC	Motor Boat Submarine Chasers
PW	Wing-in-Ground-Effect Patrol Craft
PY	Yacht
SC	Submarine Chaser (110 ft)
SCC	Submarine Chaser (control)

.

Mine Warfare Ships
 

ACM	Auxiliary Minelayer
AM	Minesweeper
AMc	Coastal Minesweeper
AMc(U)	Coastal Minesweeper (underwater locator)
CM	Minelayer
CMc	Coastal Minelayer
DM	Light Minelayer (converted destroyer)
DMS	High Speed Minesweeper (converted destroyer)
MCAC	Air Cushion Mine Countermeasures Craft
MCD	Mine Countermeasures Drone
MCM	Mine Countermeasures Ship
MCS	Mine Countermeasures Support Ship
MCT	Mine Countermeasures Conversion Trainer
MHC	Coastal Minehunter
MHI	Inshore Minehunter
ML	Minelayer
MSA	Auxiliary Minesweeper
MSAC	Air Cushion Minesweeper
MSC	Coastal Minesweeper
MSD	Drone Minesweeper
MSH	Harbor Minesweeper
MSI	Inshore Minesweeper
MSO	Ocean Minesweeper
MSR	River Minesweeper

.

Auxiliary Ships
 

AC	Collier (coaling ship)
ACS	Crane Ship
AD	Destroyer Tender
ADC	Dry Cargo Replenishment Ship
ADG	Degaussing Vessel
AE	Ammunition Ship
AF	Refrigerated Stores Ship
AFDB	Large Floating Drydock
AFDL	Small Floating Drydock
AFDM	Medium Floating Drydock
AFS	Combat Stores Ship
AG	Auxiliary, Generic/General (miscellaneous) use
AGB	Icebreaker
AGC	Amphibious Fleet Flagship
AGDS	Deep Submergence Support Ship
AGF	Fleet Flagship
AGFF	Experimental Frigate
AGH	Helicopter Support Ship
AGI	Intelligence Gathering Ship
AGM	Missile Range Instrumentation Ship
AGMR	Communications Major Relay Ship
AGOR	Oceanographic Research Ship
AGOS	Ocean Surveillance Ship
AGR	Radar Picket Ship (converted cargo ship)
AGS	Surveying Ship
AH	Hospital Ship
AHR	Riverine Hospital Ship
AK	Cargo Ship
AKA	Attack Cargo Ship
AKL	Light Cargo Ship
AKR	Roll-on/Roll-off Cargo Ship
AKV	Aircraft Cargo Ship or Ferry
AN	Net Laying (Net Tender) Ship
AO	Fleet Oiler
AOE	Fast Combat Support Ship
AOG	Gasoline Tanker
AOL	Small Oiler
AOR	Replenishment Oiler
AORL	Small Replenishment Oiler
AOT	Transport Oiler
AP	Personnel Transport Ship
APA	Attack Personnel Transport Ship
APc	Coastal Transport
APD	Troop Transport (High Speed)
APH	Transport for wounded
APL	Floating Barracks
APM	Mechanized Artillery Transport
APR	Rescue Transport
APV	Aircraft Transport
AR	Repair Ship
ARB	Repair Ship, Battle Damage
ARC	Cable Ship
ARD	Repair Dock
ARDM	Medium Repair Dock
ARL	Repair Ship, Landing Craft
ARS	Salvage Ship
ARV	Aircraft Repair Ship
ARVA	Aircraft Airframe Repair Ship
ARVE	Aircraft Engine Repair Ship
AS	Submarine Tender
ASE	Submarine Ammunition Ship
ASR	Submarine Rescue Vessel
ATA	Auxiliary Ocean Tug
ATGB	Large Icebreaking Tug
ATF	Fleet Tug
ATR	Rescue Tug
ATS	Salvage Tug
AV	Seaplane Tender
AVB	Aviation Logistics Support Ship
AVC	Catapult Lighter
AVD	Aviation Tender (Converted Destroyer)
AVP	Small Seaplane Tender
AVS	Aviation Supply Ship
AW	Distilling Ship
AX	Training Vessel (Current meaning) Auxiliary Tender, Large (Former meaning)
AXS	Sail Training Vessel
AY	VIP Yacht (Current meaning) Auxiliary Tender, Small (Former meaning)
AZ	Aerostat Tender

Note:

Attack Cargo (AKA) and Attack Personnel Transport (APA) ships differ from Cargo (AK) and Personnel Transport (AP) ships by being specially equipped to partake in amphibious landings.  The AKA and APA designations were replaced by LKA and LPA as of 1 January 1969.
 

Support Craft
 

DSRV	Deep Submergence Rescue Vehicle
DSV	Deep Submergence Vehicle
IX	Unclassified Miscellaneous
NR	Nuclear Powered Research Submersible
SDV	Swimmer Delivery Vehicle
SLWT	Side Loading Warping Tug
TWR	Torpedo Retriever
WLB	Seagoing Buoy Tender
WLM	Coastal Buoy Tender
WLI	Inland Buoy Tender
WLIC	Inland Construction Tender
WLR	River Buoy Tender
YAG	Miscellaneous Service Craft
YC	Lighter
YCF	Car Float
YCV	Aircraft Transportation Lighter
YD	Floating Crane
YDT	Diving Tender
YF	Covered Lighter
YFB	Ferry
YFN	Covered Lighter
YFNB	Large Covered Lighter
YFND	Dry Dock Companion Craft
YFNX	Special Purpose Lighter
YFP	Power Barge
YFRT	Range Tender
YFU	Harbor Utility Craft
YGN	Garbage Barge
YLC	Salvage Lift Craft
YM	Dredge
YMN	Dredge
YNG	Gate Craft
YO	Oil Barge
YOG	Gasoline Barge
YOGN	Gasoline Barge
YON	Oil Barge
YOS	Oil Storage Barge
YP	Seamanship Training Craft
YPD	Pile Driver
YPR	Parasail Training Craft
YR	Repair Barge
YRB	Repair and Berthing Barge
YRBM	Repair, Berthing, and Messing Barge
YRDH	Hull Repair Barge
YRDM	Machinery Repair Barge
YRM	Missile Retriever
YRR	Radiological Repair Barge
YRST	Salvage Craft Tender
YRT	Torpedo Retriever
YSR	Sludge Removal Barge
YTB	Large Tug
YTL	Small Tug
YTT	Torpedo Trials Craft
YW	Water Barge

.

USS Constitution

The two hundred year-old USS Constitution is unique in that she is the only ship in the USN that does not have a classification other than her name.  The Secretary of the Navy, J. William Middendorf, II, ordered her reclassification from "IX-21" to "None" effective as of 1 September 1975.  She is now listed on the Naval Vessel Register (NVR) of commissioned ships only by her name.