  The Voigt profile is one of the most used special function in optical
spectroscopy. In particle physics a version of this profile which originates
from relativistic Breit-Wigner resonance distribution often appears, however,
in the literature there is no strict derivation of its properties. The purpose
of this paper is to define properly relativistic Voigt profile and describe it
along the same way as their standard nonrelativistic counterparts.
