M91 or M-91 may refer to:
* Various iterations of the
Carcano
Carcano is the frequently used name for a series of Italian bolt-action, magazine-fed, repeating military rifles and carbines. Introduced in 1891, this rifle was chambered for the rimless 6.5×52mm Carcano round (''Cartuccia Modello 1895''). It ...
, an Italian rifle
*
M-91 (Michigan highway), a state highway in Michigan
* M91 rocket launcher, a 115mm, 45-tube, trailer mount for the
M55 rocket used by the United States Army and United States Marine Corps
*
McCarthy 91 function
The McCarthy 91 function is a recursive function, defined by the computer scientist John McCarthy as a test case for formal verification within computer science.
The McCarthy 91 function is defined as
:M(n)=\begin
n - 10, & \mboxn > 100\mbox ...
, a recursive function defined by the computer scientist John McCarthy as a test case for formal verification within computer science
*
Messier 91
Messier 91 (also known as NGC 4548 or M91) is a barred spiral galaxy that is found in the south of Coma Berenices. It is in the local supercluster and is part of the Virgo Cluster of galaxies. It is about 63 million light-years away from our ga ...
, a barred spiral galaxy about 63 million light-years away in the constellation Coma Berenices
*
Mosin Nagant Model 1891 Infantry Rifle, a Russian/Soviet rifle
* ''
Psihološko propagandni komplet M-91'', the third studio album released in 1991 by Montenegrin-Serbian musician Rambo Amadeus
*
Zastava M91
The Zastava M91 is a semi-automatic designated marksman rifle chambered in 7.62×54mmR, developed and manufactured by Zastava Arms company in Kragujevac, Serbia. Like its predecessor, the Zastava M76, the M91 is internally based upon an elongated ...
, a Serbian sniper rifle
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