  I discuss cosmological models either derived from, or inspired by, string
theory or M-theory. In particular I discuss solutions in the low-energy
effective theory and the role of the dilaton, moduli and antisymmetric form
fields in the dimensionally reduced effective action. The pre big bang model is
an attempt to use cosmological solutions to make observational predictions. I
then discuss the effective theory of gravity found in recent brane-world models
where we live on a 3-brane embedded in a five-dimensional spacetime and how the
study of cosmological perturbations may enable us to test these ideas.
