Diamond is a promising material for the modern industry. It is widely used in different applications, such as cutting tools, optical windows, heat dissipation, and semiconductors. However, these application areas require exceptionally flattened and polished diamond surfaces. Unfortunately, due to the extreme hardness and chemical inertness of diamond, the polishing of diamond is challenging. Since the 1920s, various conventional and modern mechanical, chemical, and thermal polishing techniques have been proposed and developed for finishing diamond surfaces. Therefore, to impart proper guidance on selecting a good polishing technique for production practice, this paper presents an in-depth and informative literature survey of the current research and engineering developments regarding diamond polishing. At first, a brief review of the general developments and basic material removal principles is discussed. This review concludes with a detailed analysis of each techniques’ polishing performance and critical challenges, and a discussion of the new insights and future applications of diamond polishing.