  The Wigner function, which provides a phase-space description of quantum
systems, has various applications in quantum mechanics, quantum kinetic theory,
quantum optics, radiation transport and others. The concept of Wigner function
has been extended to quantum fields, scalar and electromagnetic. Then, one
deals with the Wigner functional which gives a distribution of field and its
conjugate momentum. We introduce here the Wigner functional of fermionic fields
of the values in a Grassmann algebra. Properties of the functional are
discussed and its equation of motion, which is of the Liouville's form, is
derived.
