This article begins with a discussion on the environmental factors that induce corrosion in magnesium alloys. It reviews the factors that determine the severity of different forms of localized corrosion, namely, galvanic corrosion, corrosion fatigue, and stress-corrosion. The article discusses corrosion protection in magnesium assemblies and the protective coating systems used in corrosion protection practices. Protection schemes for specific applications and the production of novel magnesium alloys with improved corrosion resistance are also reviewed. The article concludes with a discussion on the corrosion of bulk vapor-deposited alloys and magnesium-matrix composites.