Abstract: A multi-entry fluid mixer is provided, e.g. for mixing and injecting liquid rocket propellants, which mixer has a first set of passages for receiving fluid A and a second set of passages for receiving fluid B, the passages being separated by porous walls for mixing of fluids A and B therethrough as the fluids flow through such passages and then through a porous end wall, for further mixing and then discharge, as in, say, fuel injection into the combustion chamber of a rocket. The inventive mixer can also be employed in filtrated mixing of gases or gas/liquid combinations as well as for liquid rocket propellant injection, jet engine propellant injection, chemical mixing, aerosol formation and numerous other mixing and dispersion operations.