Particle Strengthening is part of the Strengthening Mechanisms courses. Strengthening Mechanisms are part of the Ferrous Metallurgy set of courses. In this course, the principles underlying strengthening by particles will be reviewed and applied to steels. After that, the particles characterisation technique will be explained and the size and spacing effects will be treated. Then, the lattice parameter will be described and the relationship between the plane and volume will be mathematically expressed. The Orowan equation will be introduced and mathematically showed. Finally, in order to improve strength predictions, an empirical approach will be proposed.