The invention relates to a furnace slag door, comprising at least one panel which is moveable, in a mounted state of the slag door, from an opened position, in which the panel is remote from a corresponding slag discharge opening within the furnace wall to a closed position, in which the panel covers at least part of said slag discharge opening. The invention further comprises a corresponding furnace equipped with such slag door. The furnace is, in particular, an electric arc furnace (EAF) but may be as well of another type.