  We define Lie and Courant algebroids on Fr\'{e}chet manifolds. Moreover, we
construct a Dirac structure on the generalized tangent bundle of a Fr\'{e}chet
manifold and show that it inherits a Fr\'{e}chet Lie algebroid structure. We
show that the Lie algebroid cohomology of the $\bb$-cotangent bundle Lie
algebroid of a weakly symplectic Fr\'{e}chet manifold $M$ is the
Lichnerowicz-Poisson cohomology of $M$.
