  We give a definition of the Maslov fibre bundle for a lagrangian submanifold
of the cotangent bundle of a smooth manofold. This definition generelizes the
definition given, in homotopic terms, by Arnol'd for lagrangian submanifolds of
the cotangent bundle of the euclidean space and coincides with the one of
H\"{o}rmander in his works about Fourier Inegral Operators.
