Abstract: Bezout’s theorem is a fundamental result in enumerative  geometry which can be used to compute the degree of the  intersection of a finite number of varieties in general position.  In its simplest formulation it predicts the number of points of  intersection of n hypersurfaces in $\mathbb{P}^n$, which, when  counted appropriately, is given by the product of the degrees of  the defining polynomials. The goal of this talk, based on a joint  work with S. Costenoble and S. Tilson, is to illustrate how to  generalise this classical result and its proof to the case of  varieties endowed with an action of $\mathbb{Z}/2$. The solution to  this problem crucially relies on the computation for projective  spaces of a generalisation of Bredon equivariant cohomology due to  Costenoble-Waner.