MB, Mb or M. B. may refer to:
People Lee Myung-bak (born 1941), former president of South Korea Maurizio Bianchi (born 1955), Italian composer of industrial music Mario Balotelli (born 1990), Italian footballer Mahesh Babu (born 1975), an actor in Indian Telugu cinema
Arts and media Manila Bulletin, a newspaper based in the Philippines Media Blasters, an American multimedia entertainment distributor Milton Bradley Company, a board-game and sometime video-game publisher Magandang Buhay, Philippine morning talk show MusicBrainz, an online open data music database Marching band, a type of musical ensemble
Economics Mediobanca, an Italian company with Borsa Italiana stock symbol MB Multibanco, the Portuguese interbank network
Places Manitoba, province of Canada Monza and Brianza, Italy Myrtle Beach, South Carolina
Transportation Mercedes-Benz, a German brand of automobiles, buses, coaches and trucks Willys MB, the WWII-era Jeep Marunouchi Line, a subway service operated by the Tokyo Metro
Computing Megabyte (MB), a measure of information Megabit (Mb or Mbit), a measure of information MikroBitti (formerly MB), a Finnish computer magazine
Biology and chemistry Mega base pairs, a unit of measurement in genetics moisture basis, a way to measure percentages of components in a chemical composition Myoglobin, a compound in blood 2-Methylbut-3-yn-2-ol, a reagent in organic synthesis Bachelor of Medicine, an academic degree ()
Physical science Megabar (Mbar) and Millibar (mbar), a unit of pressure Body wave magnitude (m), a seismic scale Megabarn (Mb) and millibarn (mb), units of cross-sectional area Millibel (mB), a hundredth of a decibel (rarely used)
Other uses mb (digraph), a combination of letters used in spelling Medal of Bravery (Canada), a military decoration Mälarhöjden/Bredäng Hockey, a Swedish ice hockey club Muslim Brotherhood, a pan-Islamic movement