In recent years the agricultural waste or by-products has received increasing attention in the economic, scientific, social and technological areas. Rice husk (RH) is a by-product of rice milling and rice husk ash (RHA) is obtained by burning of rice husk in boiler. RHA, consists of large amount (approximately 85–95%) of amorphous silica. In past few years RH and its ash has been utilized extensively in different fields for synthesizing different materials and in wide variety of applications. The silica obtained from RHA or RH provides a potential substitute to conventional silica for the synthesis of many value-added products. This paper reviews the composition and application of Rice husk and Rice husk ash in various fields.