  We propose a six-dimensional light-front Wigner distribution for the complete
description of partonic structures of a hadron such as pion and proton, taking
advantage of the recently proposed light-front variable $\tilde{z}$ by Miller
and Brodsky. Quantities derived from the Wigner distribution contain the most
general information of partonic structures, including also new quantities
correlating longitudinal coordinate with transverse momenta or transverse
coordinates, together with spins. The new Wigner distribution can be viewed as
a relativistic version of the original Wigner distribution in hadron physics
and an extension of widely utilized five-dimensional light-front Wigner
distribution.
