A neutrino is an elementary particle and the mass of the neutrino is zero, according to the standard model of particle physics. Three flavors of neutrino exist: electron neutrinos, muon neutrinos and tau neutrinos. Neutrino oscillation is a quantum mechanical phenomenon whereby one type of neutrino flavor can later be measured to have a different flavor. This requires that neutrinos have mass. The Nobel Prize in Physics 2015 goes to neutrino oscillation. In this lecture, neutrino oscillation phenomenon will be briefly reviewed and then, various neutrino oscillation experiments will be introduced.