C3

C3, C-3, C.3, C03, C.III or C-III may refer to:

Life and biology

C₃ carbon fixation in plants
C3-convertase, an enzyme
Complement component 3, a protein of the innate immune system
Apolipoprotein C3, a human very low density lipoprotein
ATC code C03 Diuretics, a subgroup of the Anatomical Therapeutic Chemical Classification System
Castavinol C3, a natural phenolic compound found in red wines
Cytochrome-c3 hydrogenase, an enzyme
Haplogroup C-M217, called C3 in older publications
In human anatomy, C3 may refer to:
- Cervical vertebra 3, one of the cervical vertebrae of the vertebral column
- Cervical spinal nerve 3
Clinical Cell Culture, a medical technology company
C03, Malignant neoplasm of gum ICD-10 code
C3 Collaborating for Health, a health-promotion NGO
C3: an EEG electrode site according to the 10-20 system

C³, Command, control, and communications, a military concept
C-3 (plastic explosive), a plastic explosive related to C4
C-3, a United States military designation for the Ford Trimotor
the designation for several German World War I and World War II armed reconnaissance aircraft
- AEG C.III
- AGO C.III, a reconnaissance biplane of World War I
- Albatros C.III
- DFW C.III, a DFW aircraft
NAG C.III, an engine powering the Gotha G.IV aircraft
C-3, a U.S. military transport version of the Martin 4-0-4
Type C3 submarine (disambiguation), a World War II Imperial Japanese Navy cargo carrier submarine
Spanish submarine C-3
HMS C3, a 1906 British C class submarine
Type C3-class ship, a type of merchant cargo ships of United States Maritime Commission "C" design
USS C-3 (SS-14), a 1909 United States C class submarine
USS Baltimore (C-3), an 1888 protected cruiser of the United States Navy
Garda Crime and Security Branch (CSB), domestic security agency of Ireland's national police, also known as "C3"
C3 Howitzer, a lengthened variant of the M101 used by the Canadian Armed Forces

C₃, characteristic energy, in astrodynamics, a measure of the rocket energy for an interplanetary mission that requires attaining an orbital velocity above escape velocity
C₃, the chemical symbol for
- Tricarbon
- Cyclopropatriene
C3.ai, an AI company founded by Thomas Siebel
C3 linearization, a computer science algorithm for resolving the order of method resolution in multiple inheritance conditions
Delfi-C3, a Dutch CubeSat satellite
Saturn C-3, a 1960 rocket in the Saturn C series
Chaos Communication Congress, the biggest annual hacker event in Europe
Chrysler Comprehensive Compensation System, important in the development of Extreme Programming
VIA C3, a computer processor
Creatures 3, a 1999 video game
Crysis 3, a 2013 video game
Cluster 3, also known as Samba, an ESA satellite

Aeronca C-3, an American airplane
Bavarian C III, a German steam locomotive model
Bavarian C III (Ostbahn), an 1867 German steam locomotive model
Chevrolet Corvette (C3), the third production design of the Chevrolet Corvette
Circumferential Road 3 or C-3, an arterial road of Manila, Philippines
Cierva C.3, a 1921 Spanish experimental autogyro
Citroën C3, a car
Cowin C3, a car
LB&SCR C3 class, a British LB&SCR locomotive
London Buses route C3, a Transport for London contracted bus route
C3 (railcar), a bi-level railcar built by Kawasaki Railcar for the non-electrified branches of the Long Island Rail Road
Nimrod NRA/C3, a 1983 Group C racing car never achieved
Yamaha C3, a 2007 liquid cooled 49cc four-stroke motor scooter
Two different ring expressways in Japan that are numbered C3:
- Tokyo Gaikan Expressway in Tokyo, Saitama and Chiba Prefectures
- Tōkai-Kanjō Expressway in Aichi, Gifu and Mie Prefectures

C3 (classification), a para-cycling classification
C-3, Nickelodeon's old name
C³ (light novel), a 2011 Japanese light novel series and anime by Hazuki Minase
C3, a New Zealand logistics company owned by Linx Cargo Care Group
C3, the code for permission to use specific land or premises for dwellings in town and country planning in the United Kingdom
C3, the UEFA Europa League in football
C3, a standard paper size defined in ISO 216
Tippmann C-3, a pump-action paintball marker that uses propane gas
C3 Church Global, a worldwide Pentecostal denomination
C3, a class in FM radio broadcasting in North America
Argus C3, a 35mm rangefinder camera
Nokia C3 (disambiguation), various Nokia cellphones
Caldwell 3 (NGC 4236), a barred spiral galaxy in Draco
C3 policing, a methodology being employed by police to combat gangs in Springfield, Massachusetts
Nielsen ratings that include recorded programs watched three days later
Championing Community Children, a Philippine charitable organization abbreviated as C3
Charles Keating III (born 1955), American former swimmer and real estate executive
Charles III (born 1948), King of the United Kingdom and 14 other Commonwealth realms since 2022.
C-III Capital Partners, an asset management and commercial real estate services company
Hexadecimal number C3 (decimal 195)