We introduce the quasi-Hopf superalgebras which are $Z_2$ graded versions of
Drinfeld's quasi-Hopf algebras. We describe the realization of elliptic quantum
supergroups as quasi-triangular quasi-Hopf superalgebras obtained from twisting
the normal quantum supergroups by twistors which satisfy the graded shifted
cocycle condition, thus generalizing the quasi-Hopf twisting procedure to the
supersymmetric case. Two types of elliptic quantum supergroups are defined,
that is the face type $B_{q,\lambda}(G)$ and the vertex type
$A_{q,p}[\hat{sl(n|n)}]$ (and $A_{q,p}[\hat{gl(n|n)}]$), where $G$ is any
Kac-Moody superalgebra with symmetrizable generalized Cartan matrix. It appears
that the vertex type twistor can be constructed only for $U_q[\hat{sl(n|n)}]$
in a non-standard system of simple roots, all of which are fermionic.