Science

• Cubic metre (m³), a unit of volume
• Messier 3 (M3), a globular cluster in the constellation Canes Venatici

In economics:

• M3, a measure of the money supply

Computers and electronics

• Modula-3 (M3), a programming language
• M3 adapter, a Game Boy Advance movie player
• M3 Music Card, a 2007 Chinese company Meizu Flash-based MP3 player
• M3, a BBC peak programme meter standard used for measuring the volume of audio broadcasts
• M3 Simply, a Nintendo DS storage device

In video games:

• Metroid 3
• Mother 3, a Japan-only game

Transport

• BMW M3, a 1986 high performance car based on the BMW 3-Series

In roads:

• M-3 (Michigan highway), a state highway in the Detroit metropolitan area
• M3 (Cape Town), an expressway in Cape Town, South Africa
• M3 motorway, a motorway in England
• M3 motorway (Hungary), a motorway in Hungary
• M3 motorway (Northern Ireland), an urban motorway in Belfast, Northern Ireland
• M3 motorway (Pakistan)
• Russian route M3, another name for the Ukraine Highway in Russia
• M3 freeway or Eastlink in Victoria, Australia
• M3 motorway, a proposed motorway that would be an upgrade of the N3 road in the Republic of Ireland

In rail transport:

• M3 (railcar), a railcar used by the Long Island Rail Road and Metro-North Railroad, United States
• M3 Line, a part of the Bucharest Metro, Romania
• Line 3 (Budapest Metro), the third line of Budapest Metro, Hungary

In aviation:

• Miles M.3 Falcon, a 1930s British four-seat cabin monoplane
• ABSA - Aerolinhas Brasileiras's IATA airline designator

Music

• M3 Records, a record label
• Major third (M3), a type of musical interval
• Minor third (m3), a type of musical interval
• M3 (album), an album by Mushroomhead
• M3 (band), an American rock band

Other uses

In hardware:

• M3, a metric screw size

In military uses:

• M3 Bradley, an American infantry fighting vehicles
• M3 submachine gun, an American submachine gun
• M3 Half-track, an armored military vehicle
• M3 Scout Car, an American armored vehicle
• M3 Lee, an American medium tank
• M3 Grant, a medium tank that was a variant of the M3 Lee
• M3 Stuart, an American light tank
• Benelli M3 Super 90, an Italian semi-automatic shotgun
• 37 mm Gun M3, a light American anti-tank gun
• 105 mm Howitzer M3, an American light artillery piece
• M3, a code name for a United States military mission at Roosevelt Roads Naval Station in Puerto Rico
• M3 20mm cannon, a United States development of the Hispano-Suiza HS.404

In doping:

• Metribolone

See also

• 3M