  We define the notion of factorizable quasi-Hopf algebra by using a
categorical point of view. We show that the Drinfeld double $D(H)$ of any
finite dimensional quasi-Hopf algebra $H$ is factorizable, and we characterize
$D(H)$ when $H$ itself is factorizable. Finally, we prove that any finite
dimensional factorizable quasi-Hopf algebra is unimodular. In particular, we
obtain that the Drinfeld double $D(H)$ is a unimodular quasi-Hopf algebra.
