  A multi-parameter integrable deformation of the principal chiral model is
presented. The Yang-Baxter and bi-Yang-Baxter sigma-models, the principal
chiral model plus a Wess-Zumino term and the TsT transformation of the
principal chiral model are all recovered when the appropriate deformation
parameters vanish. When the Lie group is SU(2), we show that this
four-parameter integrable deformation of the SU(2) principal chiral model
corresponds to the Lukyanov model.
