Cooling air manifold splash plates and gas turbine engine systems involving such splash plates are provided. In this regard, a representative cooling air manifold splash plate (124) includes: a base (140) having an aperture (144); and an air deflector (128) supported by the base, the air deflector being positioned relative to the base to receive, from the aperture, a radial flow of gas turbine engine cooling air, the air deflector being operative to redirect at least some of the air received circumferentially.