J4

J4/J04, J-4/J-04 or J.4/J.04 may refer to:

In science and academia 

• ATC code J04 Antimycobacterials, a subgroup of the Anatomical Therapeutic Chemical Classification System
• Janko group J4, in mathematics
• S/2003 J 4, a natural satellite of Jupiter
• J04 : acute laryngitis and tracheitis ICD-10 code

In military 

• Mikoyan-Gurevich MiG-15, Chinese designation of this Soviet-made aircraft is J-4
• HMAS J4, an Australian Royal Navy submarine which saw service during World War I
• Junkers J 4, a 1917 German sesquiplane format warplane
• J4F was the U.S. Navy's designation for the Grumman Widgeon seaplane.

In transportation 

• Airmak J4, an Italian microlight aircraft design
• Auster J-4, a 1946 British single-engined two-seat high-wing touring monoplane
• Morris Commercial J4, van made from 1960–74 under the marques of Morris initially, and later, Austin and BMC
• County Route J4 (California), a road in the United States
• GS&WR Class J4, a Great Southern and Western Railway Irish steam locomotive
• Malaysia Federal Route J4, a major road in Johor, Malaysia
• Peterson J-4 Javelin, glider
• Piper J-4, a 1939 trainer aircraft
• Buffalo Airways International Air Transport Association code
• GNR Class J4, a class of British 0-6-0 steam locomotive

Other 

• J4 the Korean-South Australian 4 Js
• Jaws: The Revenge, also known Jaws 4
• Jarvan IV, a champion in League of Legends