After the primary and secondary methods of hydrocarbon production, the reservoir depletes and often relies on enhanced oil recovery techniques (EOR, a tertiary method) to reduce the residual oil saturation (S_or) to a minimum value. Amongst many methods, the chemical EOR (cEOR) technique of oil recovery is widely implemented. The cEOR technique aims to optimize mobility ratio and reduce interfacial tension (IFT) and the viscosity of in situ oil. A subclass of cEOR is surfactant flooding which uses the principle of IFT reduction to facilitate additional oil gain. This process incorporates the use of surfactants which promotes favorable wettability and forms in situ oil–water (o/w) emulsions driving the oil towards the producing well. This chapter provides insight into different classes and types of surfactants used in cEOR methods. The discussions on different surfactants are carried out broadly in terms of its effect on IFT, temperature stability, adsorption on rock matrix and effectiveness in saline environments.