An overview is presented of the nuclear data required for nuclear design analyses of fusion technology focusing on ITER, the International Thermonuclear Experimental Reactor, and IFMIF, the International Fusion Materials Irradiation Facility. The status of the available data evaluations and libraries is reviewed with regard to the required materials/nuclides and data types and, in particular, with regard to their quality as compared to differential and integral experimental data. Future development needs are identified on this basis addressing nuclear data evaluations for neutron and photon transport simulations, cross section data for activation and transmutation calculations, and co-variance data for uncertainty analyses.