  We construct the Wilson loop operator of N=6 super Chern-Simons-matter which
is invariant under half of the supercharges of the theory and is dual to the
simplest macroscopic open string in AdS_4 x CP^3. The Wilson loop couples, in
addition to the gauge and scalar fields of the theory, also to the fermions in
the bi-fundamental representation of the U(N) x U(M) gauge group. These
ingredients are naturally combined into a superconnection whose holonomy gives
the Wilson loop, which can be defined for any representation of the supergroup
U(N|M). Explicit expressions for loops supported along an infinite straight
line and along a circle are presented. Using the localization calculation of
Kapustin et al. we show that the circular loop is computed by a supermatrix
model and discuss the connection to pure Chern-Simons theory with supergroup
U(N|M).
