Industrial processes such as petroleum refining, metal fabrication, food processing and chemical manufacturing produce waste water containing free, dispersed and emulsified oil fractions. Removal of oil from waste water is essential to meet environmental discharge standards, reduce environmental impact and reuse of oil or water. Oil separators such as API (American Petroleum Institute) gravity separators, coalescing plate separators, hydro-cyclones and dissolved air floatation (DAF) units are widely use in the industries. This review study provides a comprehensive analysis of the mentioned separation technologies considering their working principles, performance characteristics, efficiency and application. The recent advancements in separation technologies, challenges, high load waste streams and compact system design are also discussed in the study. Comparative analysis has been made to highlight the differences in separation efficiency with respect to oil droplet size and waste water concentration. The review concluded by finding the operational gaps in the current separation technics and recommended the future directions for hybrid separators, smart automation and membrane integrated systems. The findings help the researchers, engineers and industry professionals in selecting appropriate separation systems for industrial waste water treatment.