MB
MB, Mb or M. B. may refer to:

Businesses and organizations
Mälarhöjden/Bredäng Hockey, a Swedish ice hockey club
Media Blasters, an American multimedia entertainment  distributor
Mediobanca, and Italian company with Borsa Italiana stock symbol MB
Mercedes-Benz, a German brand of automobiles, buses, coaches and trucks
Milton Bradley Company, a board-game and sometime video-game publisher
Muslim Brotherhood, a pan-Islamic movement

People
Lee Myung-bak (born 1941), former president of South Korea
Maurizio Bianchi or MB (born 1955), Italian composer of industrial music
Mario Balotelli (born 1990), Italian footballer
Mahesh Babu (born 1975), an actor in Indian Telugu Cinema

Science and technology
Megabyte (MB), a measure of information
Megabit (Mb or Mbit), a measure of information
MikroBitti (formerly MB), a Finnish computer magazine
Mega base pairs, a unit of measurement in genetics
Millibar, a unit of pressure
Body wave magnitude (mb), a seismic scale
Megabarn Mb and millibarn mb, units of cross-sectional area
Millibel, a hundredth of a decibel (rarely used)
Myoglobin, a compound in blood
2-Methylbut-3-yn-2-ol, a reagent in organic synthesis
Willys MB, the WWII-era Jeep

Other uses
mb (digraph), a combination of letters used in spelling
Manitoba, Canada
Medal of Bravery (Canada), a military decoration
Bachelor of Medicine, an academic degree (Medicinae Baccalaureus)
Province of Monza and Brianza, Italy
MusicBrainz, an online open data music database
Tokyo Metro Marunouchi Line, a subway service operated by the Tokyo Metro, labeled "M" on the main line, and "Mb" on the branch line.