<p>Provided is a cellulose nanofiber which enables the production of a film having excellent oxygen barrier properties and the like. The cellulose nanofiber has a crystallinity of 70% or more, a polymerization degree of 160 or less as determined by a viscosity method using a copper ethylene diamine solution and a fiber diameter of 50 nm or less. It is preferred that the cellulose nanofiber is produced by a process comprising the steps of: oxidizing a cellulose raw material with an oxidizing agent in the presence of an N-oxyl compound or the like; decreasing the viscosity of the oxidized cellulose raw material; and subjecting the oxidized cellulose raw material to a wet-mode microparticulation treatment to produce the nanofiber.</p>
