M31 may refer to:

Roadways

M31 motorway The M31 was planned as a Reading, Berkshire, Reading to M3 motorway (Great Britain), M3 motorway which was dubbed the 'M3 – M4 motorway, M4 link motorway'. It would have provided a direct high-speed route between the two motorways. The motorw ...

, a planned but unbuilt motorway in England *

M-31 (Michigan highway) M-31 was a state trunkline highway in the Lower Peninsula in the US state of Michigan. It generally ran north from Port Huron along the Lake Huron shoreline through The Thumb region before turning inland. The highway crossed The Thumb and the ...

, a former state highway in Michigan *

Hume Highway The Hume Highway, including the sections now known as the Hume Freeway and the Hume Motorway, is one of Australia's major inter-city national highways, running for between Melbourne in the southwest and Sydney in the northeast. Upgrading of t ...

in Australia, designated "M31" *

M31 motorway (Hungary) The M31 motorway () is a motorway in Hungary, that runs between the M0 motorway at Nagytarcsa and the M3 motorway at Gödöllő. Municipalities The M31 motorway runs through the following municipalities: * Pest County: Budapest, Nagytarcsa, ...

, a short motorway section near Budapest, Hungary * M31 (Cape Town), a Metropolitan Route in Cape Town, South Africa *

M31 (Johannesburg) The M31 is a metropolitan route in the City of Johannesburg, South Africa. The road connects the southern suburbs of Alberton with Johannesburg's northern suburbs. The route's eastern bypass in the Johannesburg CBD connects the M2 motorway at ...

, a Metropolitan Route in Johannesburg, South Africa * M31 (Pretoria), a Metropolitan Route in Pretoria, South Africa *

M31 (Durban) Ethekwini (Durban metropolitan area), like most South African metropolitan areas, uses metropolitan or "M" routes for important intra-city routes, a layer below national (N) roads and regional (R) roads. Each city's M roads are independently ...

, a Metropolitan Route in Durban, South Africa

Military

* Suomi M-31 SMG, a Finnish WWII-era submachine gun *

M31 HEAT rifle grenade The M31 HEAT is a fin-stabilized anti-tank rifle grenade designed in the late 1950s to replace the Belgian ENERGA rifle grenade which was adopted by the US Army and US Marines as an emergency stop-gap measure during the Korean War. Like the EN ...

* M31 Recovery Vehicle based on the

M3 Lee The M3 Lee, officially Medium Tank, M3, was an American medium tank used during World War II. The turret was produced in two different forms, one for US needs and one modified to British requirements to place the radio next to the commander. ...

tank * M31 rocket, an alternate designation for the

MGR-1 Honest John The MGR-1 Honest John rocket was the first nuclear weapon, nuclear-capable surface-to-surface rocket in the United States arsenal.The first nuclear-authorized ''guided'' missile was the MGM-5 Corporal. Originally designated Artillery Rocket XM31 ...

, a United States military rocket * M31 (missile), for a multiple-launch rocket system (MLRS) * M31 is the pennant number for HMS ''Cattistock'', a Hunt-class mine countermeasures vessel

Other

* M₃₁ = 0x7FFFFFFF =

2147483647 The number 2147483647 is the eighth Mersenne prime, equal to 231 − 1. It is one of only four known double Mersenne primes. The primality of this number was proven by Leonhard Euler, who reported the proof in a letter to Daniel Ber ...

, the eighth Mersenne prime number *

M31 (New York City bus) The M31 and M57 bus routes constitute the 57th Street Crosstown Line, a public transit line in Manhattan, New York City, running primarily along 57th Street (Manhattan), 57th Street. The M31 runs between 11th Avenue (Manhattan), 11th Avenue and ...

, a New York City Bus route in Manhattan * ''M31: A Family Romance'', a novel by writer Stephen Wright *

Messier 31 Messier may refer to: People with the surname *Ashley Messier (born 2002), Canadian ice hockey player *Charles Messier (1730–1817), French astronomer *Doug Messier (born 1936), Canadian ice hockey player and coach *Éric Messier (born 1973), Cana ...

(M31), a spiral galaxy also called the Andromeda Galaxy *

Samsung Galaxy M31 The Samsung Galaxy M31 is an Android smartphone manufactured by Samsung Electronics as part of the Galaxy M series. It was unveiled on 25 February 2020. Its key features include a 6.4 inch Super AMOLED display, a quad-camera setup and a 6000&nb ...

, an Android based smartphone *

Remington Model 31 The Remington Model 31 is a pump-action shotgun that competed with the Winchester Model 1912 for the American sporting arms market. Produced from 1931 to 1949, it superseded the John Pedersen-designed Models 10 and 29, and the John Browning-d ...

, a pump-action shotgun made by

Remington Arms Remington Arms Company, LLC, was an American firearms manufacturer, manufacturer of firearms and ammunition. It was formerly owned by the Remington Outdoor Company, which went bankrupt in 2020 with its lines of business sold to several purchase ...

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