It is well known that magnesium alloys reinforced with ceramic particles of micro-scale sizes give increased hardness and wear resistance. However, such particles need to be smaller to improve the strength, ductility and creep resistance of alloys. The optimum size of particles for Orowan strengthening is a diameter less than 100 nm. Not only the size of particles, but also their chemical composition and the composition of the alloy are important for the beneficial effect of nanoparticles. The mechanical properties can be tailored with much fewer nanoparticles compared to microparticles, because the interparticle spacing is much smaller. However, with large surface areas compared to their weight and low wettability, any deagglom-eration of the nanoparticles in a magnesium melt is difficult to achieve and so requires additional processing, such as by electromagnetic or ultrasound-assisted stirring. This paper presents a short review and some original work on ceramic nanoparticle reinforced magnesium alloys and their properties.