We give an exposition of the theory of invariant manifolds around a fixed point, in the case of time-discrete, analytic dynamical systems over a complete ultrametric field K. Typically, we consider an analytic manifold M modelled on an ultrametric Banach space over K, an analytic diffeomorphism f : M → M , and a fixed point p of f . Under suitable assumptions on the tangent map T p (f ), we construct a centrestable manifold, a centre manifold, respectively, an a-stable manifold around p, for a given real number a ∈ ]0, 1].Classification: 37D10 (Primary) 46S10, 26E30 (Secondary)