It is shown that the recently discovered giant negative magnetoresistance (GMR) effects in ferromagnetic La1−xMxMnO3 (M=Ca,Sr,Ba) are compatible with the existence of high Tc superconductivity in c-axis oriented YBa2Cu3O7/La0.67Ba0.33MnO3 superlattices. From magnetoresistivity measurements we deduce that above Tc the giant GMR persists up to room temperature. Below Tc the superlattices show a quasi-two-dimensional superconductivity of the YBa2Cu3O7 layers coexisting with magnetism in the La0.67Ba0.33MnO3 layers.