The type of oil and gas reservoir is the foundation for understanding the distribution patterns of oil and gas and is one of the key elements that must be understood in oil and gas exploration. Oil and gas reservoirs are influenced by a variety of factors, including reservoir shape, trap type, reservoir type, seal type, and the phase state of oil and gas, which leads to a highly complex classification scheme for oil and gas reservoirs. Among these, classification based on trap genesis reflects the scientific and practical nature of reservoir classification and is widely used in oil and gas exploration. This chapter mainly classifies oil and gas reservoirs according to trap genesis, dividing them into five major categories: structural, stratigraphic, lithologic, composite, and special types of oil and gas reservoirs, and introduces the characteristics of each type of reservoir.