In recent years, great attention has been paid to the development of ceramic membranes. Ceramic membranes have extremely high chemical, thermal, and mechanical stability. This makes them suitable for many applications in the chemical and pharmaceutical industry or in water and wastewater treatments, especially for high temperature, extreme acidity or alkalinity, and high-pressure operations where the application precludes the use of existing polymeric and other inorganic membranes. The fundamental separation mechanism varies according to the membrane type. This entry is focused on ceramic membranes that work at the molecular level to separate gases and liquids. This is an emerging field for membrane technology that will transfer the benefits of durability experienced in separation of larger species (i.e., microfiltration) to separation at the molecular scale where few membrane units are commercially available. Transport mechanisms and modeling of ceramic membrane processes are also discussed.