A heat shield (44) for an external component, such as a gearbox (42), of a gas turbine engine (20) for limiting heat transfer from the engine (20) to the external component is disclosed. The heat shield (44) may be formed to the shape of the gearbox (42) to reduce the geometric envelope of the gearbox (42) and heat shield (44). The heat shield (44) may be formed by a thin thermal insulation core (50) surrounded by a metal sheet (51). The small thickness of the heat shield (44) also reduces the geometric envelope of the heat shield (44). Since no extra equipment is needed to provide cooling fluid to the gearbox (42), the heat shield (44) reduces the overall weight of the gas turbine engine (20) as well.