MCB or mcb may refer to:

• Molecular and Cellular Biology, a scientific journal published by the American Society for Microbiology
• Monochlorobenzene, an aromatic organic compound

• Miniature circuit breaker, a relatively small electrical circuit breaker fitted in consumer units and small distribution boards

• Mauritius Commercial Bank, the oldest and largest banking institution in Mauritius
• Muslim Commercial Bank, former name of MCB Bank Limited, a network of banks in Pakistan

• Maidenhead Citadel Band of The Salvation Army
• Management Consultants Bradford, previous name of a scholarly publisher of academic journals and books in Britain, now renamed Emerald Group Publishing
• Master Car Builders coupler, or Janney coupler, a type railroad coupling widely used in North America and elsewhere.
• MCB Tower, a skyscraper in Pakistan, owned by MCB Bank Limited
• McComb (Amtrak station), Mississippi, United States; Amtrak station code MCB
• Methodist College Belfast, a voluntary grammar school in Belfast, Northern Ireland
• The Muslim Council of Britain, an organisation promoting unity among traditional Muslims in the United Kingdom
• Movimiento Continental Bolivariano, Spanish name of the Bolivarian Continental Movement, a left-wing political movement in Latin America