Keff

Keff may refer to:
 * an abbreviation for the reactivity coefficient k-effective (written as keff), the effective neutron multiplication factor within an assembly of fissile material, in nuclear reactor theory
 * Kerala Farmers Federation, an Indian organisation
 * Keff McCulloch, a British composer
 * Keff Ratcliffe, a Welsh musician and the former guitarist for the American band  LA Guns.