We investigate the link between kinetic equations (including Boltzmann with or
without cutoff assumption and Landau equations) and the incompressible
Navier–Stokes equation. We work with strong solutions and we treat all the cases in a
unified framework. The main purpose of this work is to be as accurate as possible in
terms of functional spaces. More precisely, it is well known that the Navier–Stokes
equation can be solved in a lower regularity setting (in the space variable) than
kinetic equations. Our main result allows to get a rigorous link between solutions
to the Navier–Stokes equation with such low regularity data and kinetic
equations.