The abbreviation KB or kb can refer to:
kilobyte (kB or KB), equal to 1,000 bytes or 1024 bytes depending on context, or kibibyte (KiB), equal to 1,024 bytes.
kilobit (kbit), equal to 1,000 bits or 1024 bits (depending on context), or kibibit (Kibit), equal to 1,024 bits.
Knowledge base, a collection of knowledge helping users with a given product.
Knowledge Bowl, an interdisciplinary academic competition.
Keyboard, such as:

• Alphanumeric keyboard, a data entry device.
  Keyboard instrument, a musical instrument.
  Base dissociation constant (K_b), the constant which refers to the equilibrium in which a base reacts with H₂O to form a corresponding conjugate acid and OH.
  Boltzmann constant (k_b), the physical constant which relates temperature to energy.
  Knight of the Bath, a former rank (before 1847) of the Order of the Bath, a part of the British honours system; sometimes also refers to Knight Bachelor.
  King's Bench, an ancient English court, or the legal citation denoting a case in such court.
  Kilo-base pair (kb or kbp), a unit of measurement of DNA or RNA length used in genetics, equal to 1,000 nucleotides.
  KB Home, a major American home builder.
  KB Toys, a United States toy retail chain.
  K&B, a local drug store in New Orleans, Louisiana, that was bought by Rite Aid.
  Swedish Royal Library (Kungliga Biblioteket), the national library of Sweden.
  Komercni Banka, a bank in the Czech Republic.
  Dutch Royal Library (Koninklijke Bibliotheek), the national library of the Netherlands.
  Kookmin Bank, the largest bank in South Korea.
  KB Banki, a bank in Iceland.
  Kjøbenhavns Boldklub, Continental Europe's oldest football club founded April 26, 1876, in Copenhagen.
  Druk Air (IATA code: KB), the national airline of Bhutan.
  Kobe Bryant, an NBA superstar.
  NASCAR driver Kurt Busch or his brother Kyle
  ebullioscopic constant (K_b), the constant which relates molality to boiling-point elevation.