The United States Navy uses hull classification symbols (sometimes called hull codes) to identify the types of its ships. The Royal Navy and some European and Commonwealth navies use a somewhat analogous system of Pennant numbers.

The combination of symbol and hull number identify a modern Navy ship uniquely. A heavily modified or repurposed ship may receive a new symbol, and either retain the hull number or receive a new one. Also, the system of symbols has changed a number of times since it was introduced in 1907, so ships' symbols sometimes change without anything being done to the physical ship.Derdall and DiGiulian, (section: ''Nomenclature history'')

Many of the symbols listed here are not presently in use. The Naval Vessel Register maintains an online database of US Navy ships.

The 1975 ship reclassification of cruisers, frigates, and ocean escorts brought US Navy classifications into line with other nations' classifications, and eliminated the perceived "cruiser gap" with the Soviet Navy.

If a ship's hull classification symbol begins with "W," it is a ship of the United States Coast Guard. If it begins with "T-", it is part of the Military Sealift Command and has a primarily civilian crew.

Aircraft Carrier type

All ships designed primarily for the purpose of conducting combat operations by aircraft which engage in attacks against airborne, surface, sub-surface and shore targets. The "CV" designation was originally derived from cruisers, since aircraft carriers were seen as an extension of the sea control and denial mission of cruisers. The "V" designation for heavier than air craft comes from the French verb "''Voler''" (to fly).''United States Naval Aviation 1910-1995'', Appendix 16 Contrary to popular belief, the "CV" hull classification symbol does not stand for "Carrier Vessel". Since 1935, "CV" has been a two-letter, unitary hull classification symbol, meaning "aircraft carrier." Aircraft carriers are designated in two sequences: The first, which has run from CV-1 USS ''Langley'' to the very latest ships, and the second, the CVE escort carrier sequence, ran from CVE-1 ''Long Island'' to CVE-128 ''Okinawa'' before being discontinued.

AV: Seaplane Tender (retired)

AVG: Auxiliary Aircraft Ferry (Escort carrier) (1941-2)

AVD: Destroyer Seaplane Tender (retired)

AVP: Patrol Seaplane Tender (retired)

ACV: Auxiliary Aircraft Carrier (Escort carrier) (1942)

CV: Fleet Aircraft Carrier (1921-1975), Multi-purpose Aircraft Carrier (1975-present)

CVA: Attack Aircraft Carrier (category merged into CV, 30 June 1975)

CVAN: Attack Aircraft Carrier, Nuclear (category merged into CVN, 30 June 1975)

CVB: Large Aircraft Carrier (category merged into CVA, 1952)

CVE: Escort aircraft carrier (retired) (1943-retirement of type)

CVHA: Assault Helicopter Aircraft Carrier (retired in favor of various L-series amphibious assault ship hull codes)

CVHE: Escort Helicopter Aircraft Carrier (retired)

CVL: Light aircraft carrier (retired)

CVN: Multi-purpose Aircraft Carrier (Nuclear-Propulsion)

CVS: Antisubmarine Aircraft Carrier (retired)

CVT: Training Aircraft Carrier (changed to AVT (Auxiliary))

CVU: Utility Aircraft Carrier (retired)

Surface Combatant type

Surface ships which are designed primarily to engage enemy forces on the high seas. The primary surface combatants are battleships, cruisers and destroyers. Battleships are very heavily armed and armored; cruisers moderately so; destroyers and smaller warships, less so. Before 1920, ships were called " no. X," with the type fully pronounced. The types were commonly abbreviated in ship lists to "B-X," "C-X," "D-X" et cetera - for example, before 1920, USS Minnesota (BB-22) would have been called "USS ''Minnesota'', Battleship number 22" verbally and "USS ''Minnesota'', B-22" in writing. After 1920, the ship's name would have been both written and pronounced "USS ''Minnesota'' (BB-22)" In generally decreasing size, the types are:

B: Battleship (pre-1920)

BB: Battleship

BBG: Guided Missile Battleship or Arsenal Ship (theoretical only, never assigned)

BM: Monitor (1920-retirement)

ACR: Armored Cruiser (pre-1920)

C: Cruiser (pre-1920 Protected Cruisers and Peace Cruisers)

CA: (first series) Cruiser (retired, composed all surviving pre-1920 Protected and Peace Cruisers)

CA: (second series) Heavy Cruiser, category later renamed Gun Cruiser (retired)

CAG: Guided Missile Heavy Cruiser (retired)

CB: Large cruiser (retired)

CBC: Large Command Cruiser (retired, never used operationally)

CC: Battlecruiser (retired, never used operationally)

CC: (second usage) Command Cruiser (retired)

CG: Guided Missile Cruiser

CGN: Guided Missile Cruiser (Nuclear-Propulsion)

CL: Light Cruiser (retired)

CLAA: Antiaircraft Cruiser (retired)

CLG: Guided Missile Light Cruiser (retired)

CLGN: Guided Missile Light Cruiser (Nuclear-Propulsion) (retired)

CLK: Hunter-Killer Cruiser (abolished 1951)

CS: Scout Cruiser (retired)

CSGN: Strike Cruiser (Nuclear-Propulsion)

D: Destroyer (pre-1920)

DD: Destroyer

DDE: Escort Destroyer (not to be confused with Destroyer Escort, DE - an Escort Destroyer, DDE, was a Destroyer, DD, converted for antisubmarine warfare) (category abolished 1962)

DDG: Guided Missile Destroyer

DDK: Hunter-Killer Destroyer (category merged into DDE, 4 March 1950)

DDR: Radar Picket Destroyer (retired)

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DE: Destroyer Escort (World War II, later became Ocean escort)

DE: Ocean escort (abolished 30 June 1975)

DEG: Guided Missile Ocean Escort (abolished 30 June 1975)

DER: Radar Picket Destroyer Escort (abolished 30 June 1975)

|There were two distinct breeds of DE, the World War II Destroyer Escorts (some of which were converted to DERs) and the postwar DE/DEG classes, which were known as Ocean Escorts despite carrying the same type symbol as the WWII Destroyer Escorts. All DEs, DEGs, and DERs were reclassified as FFs, FFGs, or FFRs, 30 June 1975.
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DL: Destroyer Leader (later Frigate) (retired)

DLG: Guided Missile Frigate (abolished 30 June 1975)

DLGN: Guided Missile Frigate (Nuclear-Propulsion) (abolished 30 June 1975)

|The DL category was established in 1951 with the abolition of the CLK category. CLK 1 became DL 1 and DD 927-930 became DL 2-5. By the mid-1950s the term Destroyer Leader had been dropped in favor of Frigate. Most DLGs and DLGNs were reclassified as CGs and CGNs, 30 June 1975. However, DLG 6-15 became DDG 37-46. The old DLs were already gone by that time.

DM: Destroyer Minelayer (retired)

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FF: Frigate (retired)

FFG: Guided Missile Frigate

FFL: Light Frigate

FFR: Radar Picket Frigate (retired)

FFT: Frigate (Reserve Training) (retired)

|The FF, FFG, and FFR designations were established 30 June 1975 as new type symbols for ex-DEs, DEGs, and DERs. The first new-build ships to carry the FF/FFG designation were the ''Oliver Hazard Perry'' (FFG-7) class frigates. A new series of frigate-size warships for shallow-water combat at expense of battlegroup performance is under production:

K: Corvette (retired)

LCS: Littoral Combat Ship

M: Monitor (1880s-1920)

Submarine type

All self-propelled submersible types (usually started with SS meaning submersible ship) regardless of whether employed as combatant, auxiliary, or research and development vehicles which have at least a residual combat capability.

SC: Cruiser Submarine (retired)

SF: Fleet Submarine (retired)

SM: Submarine Minelayer (retired)

SS: Submarine (U.S. designator for diesel-electric attack submarines; Royal Navy uses SSK)

SSA: Cargo Submarine (retired)

SSC: Coastal Submarine (over 150 tons)

SSP: Submarine (Diesel Air-Independent Power) (Sometimes seen as "Air-Independent Propulsion" but as with SSNs, the AIP system is providing power rather than propulsion. SSI is also used, but rarely.){{cite journal | last = Buff | first = Joe | authorlink = Joe Buff

| year = 2007 | month = June | title = Subs in the Littoral: Diesels Just Blowing Smoke? | journal = Proceedings of the Naval Institute
| volume = 133 | issue = 6 | pages = 40-43 | issn = 0041-798X | url = http://www.usni.org/ | accessdate = 2007-06-13
| quote = Diesel AIP boats are known as SSIs, differentiating them from purely diesel-electric-powered hunter-killer subs, or SSKs. }}

SSK: Hunter-Killer Submarine (Royal Navy designation for diesel-electric attack submarines rather than SS)

SSM: Midget Submarine (under 150 tons)

SSN: Attack Submarine (Nuclear-Powered)

SSBN: Ballistic Missile Submarine (Nuclear-Powered)

SSG: Guided Missile Submarine (retired)

SSGN: Guided Missile Submarine (Nuclear-Powered)

SSO: Submarine Oiler (retired)

SSP: Submarine Transport (retired)

SSR: Radar Picket Submarine (retired)

SSRN: Radar Picket Submarine (Nuclear-Powered) (retired)

SST: Training Submarine (retired)

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AGSS: Auxiliary Submarine

AOSS: Submarine Oiler (retired)

ASSP: Transport Submarine (retired)

APSS: Transport Submarine (retired)

LPSS: Amphibious Transport Submarine (retired)

|SSP, ASSP, APSS, and LPSS were all the same type, redesignated over the years.

IXSS: Unclassified Miscellaneous Submarine

MTS: Moored Training Ship (Navy Nuclear Prototype School Training Platform; Reconditioned SSBN's)

Patrol Combatant type

Combatants whose mission may extend beyond coastal duties and whose characteristics include adequate endurance and sea keeping providing a capability for operations exceeding 48 hours on the high seas without support. Brown Water Navy/Riverine Forces, Vietnam War; Few in service today.

PC: Coastal Patrol, originally Sub Chaser

PCF: Patrol Craft, Fast; Swift Boat, Brown Water Navy (Vietnam)

PE: Eagle Boat of World War I

PF: World War II Frigate, Based on British River class.

PFG: Original designation of USS ''Oliver Hazard Perry'' (FFG-7)

PG: Gunboat, later Patrol combatant

PT: Motor Torpedo Boat (World War II)

PTG: Guided Missile Patrol Boat

PGH: Patrol Combatant, Hydrofoil

PHM: Patrol, Hydrofoil Missile

PBR: Patrol Boat, River, Brown Water Navy (Pibber or PBR-Vietnam)

Monitor: Heavily gunned riverine boat, Brown Water Navy (Vietnam)

ASPB: Assault Support Patrol Boat, "Alpha Boat", Brown Water Navy; also used as riverine minesweeper (Vietnam)

PACV: Patrol, Air Cushion Craft, Brown Water Navy (Vietnam)

Amphibious Warfare type

All ships having organic capability for amphibious assault and which have characteristics enabling long duration operations on the high seas. There are two classifications of craft here, the amphibious assault ships, built to cross oceans, and Landing Craft, to take troops from the ship to the shore in an invasion.

Ships

AKA: Attack Cargo Ship (out of commission)

APA: Attack Transport (out of commission)

APD: High speed transport Converted Destroyer or Destroyer Escort (out of commission)

LCC: Amphibious Command Ship

LHA: Amphibious Assault Ship (Attack/Assault, i.e. attack aircraft)

LHD: Amphibious Assault Ship (Dock, similar to LHA but emphasis on Landing Craft ability)

LKA: Amphibious Cargo Ship (out of commission)

LPA: Landing Platform, Amphibious

LPD: Amphibious Transport, Dock (aka Landing Platform, Dock)

LPH: Landing Platform, Helicopter (out of commission)

LSD: Landing Ship, Dock

LSH: Landing Ship, Heavy

LSIL: Landing Ship, Infantry (Large) (formerly LCIL)

LSL: Landing Ship, Logistics

LSM: Landing Ship, Medium

LSM(R): Landing Ship, Medium (Rocket)

LSSL: Landing Ship, Support (Large) (formerly LCSL)

LST: Landing Ship, Tank

LSV: Landing Ship Vehicle

Landing Craft

LCA: Landing Craft, Assault

LCAC: Landing Craft, Air Cushioned

LCFF: (Flotilla Flagship)

LCH: Landing Craft, Heavy

LCI(G)(L)(M)(R): Landing Craft, Infantry (Gunboat) (Large) (Mortar) (Rocket) (World War II era)

LCL: Landing Craft, Logistics (UK)

LCM: Landing Craft, Mechanized

LCP: Landing Craft, Personnel

LCPA: TBD

LCS(L): Landing Craft, Support (Large) (World War II era)

LCT: Landing Craft, Tank (World War II era)

LCU: Landing Craft, Utility

LCVP: Landing Craft, Vehicle and Personnel

Support type

A grouping of ships designed to operate in the open ocean in a variety of sea states to provide general support to either combatant forces or shore based establishments. (Includes smaller auxiliaries which by the nature of their duties, leave inshore waters).

ACS: Auxiliary Crane Ship

AG: Miscellaneous Auxiliary

AGDE: Testing Ocean Escort

AGDS: Deep Submergence Support Ship

AGER: Environmental Research Ship

AGF: Miscellaneous Command Ship

AGFF Testing Frigate

AGM: Missile Range Instrumentation Ship

AGOR: Oceanographic Research Ship

AGOS: Ocean Surveillance Ship

AGS: Surveying Ship

AGSS: Auxiliary Research Submarine

AGTR: Technical research ship

AH: Hospital ship

AK: Cargo Ship

AKR: Vehicle Cargo Ship

AKS: Store Issue Ship

AOG: Gasoline Tanker

AOT: Transport Oiler

AP: Transport

ARC: Cable Repair Ship

APL: Barracks Craft

ARL: Small Repair Ship

ARS: Salvage Ship

AS: Submarine tender

ASR: Submarine Rescue Ship

AT: Ocean-Going Tug

ATA: Auxiliary Ocean Tug

ATF: Fleet Ocean Tug

ATS: Salvage and Rescue Ship

AVB: Aviation Logistics Support Ship

AVT: Auxiliary Aircraft Landing Training Ship

Service Type Craft

A grouping of navy-subordinated craft (including non-self-propelled) designed to provide general support to either combatant forces or shore-based establishments. The suffix "N" refers to non-self propelled variants.

AB: Crane Ship

AFDB: Large Auxiliary Floating Dry Dock

AFDL: Small Auxiliary Floating Dry Dock

AFDM: Medium Auxiliary Floating Dry Dock

APB: Self-Propelled Barracks Ship

APL: Barracks Craft

ARD: Auxiliary Repair Dry Dock

ARDM: Medium Auxiliary Repair Dry Dock http://en.wikipedia.org/wiki/USS_Oak_Ridge_%28ARDM-1%29

ATA: Auxiliary Ocean Tug

DSRV: Deep Submergence Rescue Vehicle

DSV: Deep Submergence Vehicle

NR: Submersible Research Vehicle

YC: Open Lighter

YCF: Car Float

YCV: Aircraft Transportation Lighter

YD: Floating Crane

YDT: Diving Tender

YF: Covered Lighter

YFB: Ferry Boat or Launch

YFD: Yard Floating Dry Dock

YFN: Covered Lighter (non-self propelled)

YFNB: Large Covered Lighter (non-self propelled)

YFND: Dry Dock Companion Craft (non-self propelled)

YFNX: Lighter (Special purpose) (non-self propelled)

YFP: Floating Power Barge

YFR: Refrigerated Cover Lighter

YFRN: Refrigerated Covered Lighter (non-self propelled)

YFRT: Range Tender

YFU: Harbor Utility Craft

YG: Garbage Lighter

YGN: Garbage Lighter (non-self propelled)

YLC: Salvage Lift Craft

YM: Dredge

YMN: Dredge (non-self propelled)

YNG: Gate Craft

YNT: Net Tender

YO: Fuel Oil Barge

YOG: Gasoline Barge

YOGN: Gasoline Barge (non-self propelled)

YON: Fuel Oil Barge (non-self propelled)

YOS: Oil Storage Barge

YP: Patrol Craft, Training

YPD: Floating Pile Driver

YR: Floating Workshop

YRB: Repair and Berthing Barge

YRBM: Repair, Berthing and Messing Barge

YRDH: Floating Dry Dock Workshop (Hull)

YRDM: Floating Dry Dock Workshop (Machine)

YRR: Radiological Repair Barge

YRST: Salvage Craft Tender

YSD: Seaplane Wrecking Derrick

YSR: Sludge Removal Barge

YT: Harbor Tug (craft later assigned YTB, YTL, or YTM classifications)

YTB: Large Harbor Tug

YTL: Small Harbor Tug

YTM: Medium Harbor Tug

YTT: Torpedo Trials Craft

YW: Water Barge

YWN: Water Barge (non-self propelled)

IX: Unclassified Miscellaneous Unit

X: Submersible Craft

"none": To honor her unique historical status, USS ''Constitution'', formerly IX 21, was reclassified to "none," effective 1 September 1975.