Quenched and partitioned (Q&P) steels are complex, sophisticated materials, with carefully-selected chemical compositions and multiphase microstructures resulting from precisely controlled heating and cooling processes. The concept of the quenching and partitioning process was first proposed in 2003 by Speer and his colleagues. The key treatment parameters include annealing temperature, quenching temperature, partitioning temperature and time. Manipulation with these parameters along with the steel chemistry leads to a variety of multiphase microstructures showing a wide range of properties. The principles of microstructural design in Q&P steels for improvement of their mechanical strength with no (or very low) reduction of tensile ductility have been understood to a satisfactory level by now. However, the steel performance for a specific industrial application is not governed just by its mechanical strength and ductility under uniaxial tension. Enhanced mechanical properties need to be combined with improved performance properties (such as fatigue, fracture, weldability, galvanability, etc.), which have been studied to a lesser extent. For this Special Issue in Metals, we welcome research articles and reviews addressing theoretical and experimental design of steels and Q&P process, microstructure of Q&P treated steels, their mechanical and performance properties, Q&P process–microstructure –properties relationship, as well as examples of their industrial applications. The Special Issue is oriented to researchers from universities and industrial research centers and to steel producers directly involved in the production and product development.@en