F91 may refer to :
*
F91 Dudelange
F91 Dudelange (; lb, F91 Diddeleng, italic=no, ) is a Luxembourger professional football club based in Dudelange which plays in the Luxembourg National Division.
It was formed in 1991 as a merger between three teams in the town: Alliance Dud ...
, a football club, based in Dudelange in southern Luxembourg
* ''
Mobile Suit Gundam F91'', a 1991 animated film
*
HMS Brazen (F91), a 1981 British Royal Navy Type 22 frigate
*
HMS Murray (F91)
HMS ''Murray'' (F91) was one of a dozen Blackwood-class frigate (also known as the Type 14 class) of second-rate anti-submarine frigates built for the Royal Navy in the 1950s. She was named for George Murray, who served during the late 18t ...
, a British Royal Navy Blackwood class second-rate anti-submarine frigate
* Republic
XF-91 Thunderceptor
The Republic XF-91 Thunderceptor (originally designated XP-91) is a mixed-propulsion prototype interceptor aircraft, developed by Republic Aviation. The aircraft would use a jet engine for most flight, and a cluster of four small rocket engines ...
, a rocket-jet hybrid interceptor
*
Casio F-91W
The Casio F-91W is a digital watch manufactured by Japanese electronics company Casio. Introduced in 1989 as a successor of the F-87W, it is popular for its low price and long battery life. As of 2011, annual production of the watch is 3 mi ...
, a common and inexpensive digital watch, claimed by some to be associated with
terrorism
Terrorism, in its broadest sense, is the use of criminal violence to provoke a state of terror or fear, mostly with the intention to achieve political or religious aims. The term is used in this regard primarily to refer to intentional violen ...
* The
McCarthy 91 function, a recursively defined mathematical function
and also:
*
Conduct disorders ICD-10 code
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