  Given any pointed CW complex (X,x), it is well known that the fondamental
group of X pointed at x is naturally isomorphic to the automorphism group of
the functor which associates to a locally constant sheaf on X its fibre at x.
The purpose of this work is to generalize this fact to higher homotopy. For
this we introduce the (infinite) category of locally constant stacks on X, and
we prove that the loop-space of endomorphisms of its fibre functor at x is
naturally equivalent to the loop space of X based at x.
