This article begins with an overview of classes and applications of gray iron. It discusses the castability of gray iron in terms of section sensitivity and fluidity. The article provides information on the dimensions of prevailing sections recommended for gray irons and reviews the properties and specifications of test bar. It discusses the properties of gray iron, such as fatigue limit, pressure tightness, impact resistance, machinability, and dimensional stability, at both room and elevated temperature. Wear behavior of gray iron castings during sliding contact under conditions of normal lubrication is also discussed. The article reviews the use of alloys and heat treatment to modify as-cast properties. It concludes with information on physical properties of gray iron castings.