J1, J01, J.I or J-1 may refer to:

• J-I, a Japanese launcher
• J1 type submarine, a WWII Imperial Japanese Navy cruiser submarines class
• J-1 visa, a type of U.S. visa for exchange visitors (e.g. students coming to the USA for an internship)
• J-1 World Heavyweight Championship, a wrestling competition
• AEG J.I, a World War I German ground attack aircraft
• Albatros J.I, a 1917 German ground-attack single-engine biplane aircraft
• ATC code J01, a section of the Anatomical Therapeutic Chemical Classification System
• DSER Class J1, a Dublin and South Eastern Railway Irish steam locomotive
• Haplogroup J1 (Y-DNA), a Y-DNA haplogroup
• Janko group J1 in mathematics
• Junkers J 1, a 1916 German aircraft
• Junkers J.I, a 1917 German aircraft
• Lawrance J-1, a early 1920s engine used in American aircrafts
• LB&SCR J1 class, a British LB&SCR locomotive
• PRR J1, an American PRR steam locomotive
• S/2003 J 1, a former name for Eukelade, a retrograde irregular satellite of Jupiter

and also :

• a shorthand for J. League Division 1 in Japanese Football
• J01 : acute sinusitis ICD-10 code

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