The abbreviation KB or kb can refer to:

*Kilobit (kb), a unit of information used, for example, to quantify computer memory or storage capacity
*Kilobyte (kB), a unit of information used, for example, to quantify computer memory or storage capacity

*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
*Counter-electromotive force constant ("k_b"), a parameter in motor dynamics
*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
*"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
*Kingsbrook College (K.B), a rural comprehensive school located in Deanshanger, often abbreviated to K.B
*Drukair (IATA code: "KB"), the national airline of Bhutan
* Kobe Bryant, professional basketball player
* Kurt Busch, NASCAR driver
* Kine Bud, a potent strain of marijuana often referred to as KB
* Kauri-butanol, (Kb value) a measure of solvent performance
*KB Series Truck, a truck produced by International Harvester
* King's Bounty, a 1990 computer game by New World Computing, or , its 2008 sequel.