Trademarks and service marks have become indispensable for entities in today's world as they add value to their proprietors' business and reputation. Thanks to advancements in telecommunication and online advertising technologies, the use and dissemination of these marks have become easier and more widespread. This, however, also had a negative impact on marks, in that, it became easier to take unfair advantage of such marks, even more so, if these are well-known marks. In line with this, a special protection regime is granted to well-known marks, by national, regional and international legal instruments such as the Paris Convention and the TRIPS Agreement. These have been drafted in a way that confers well-known marks a special position among other marks in the sense that they are held exempt from principles such as the principles of territoriality, class-based protection and the ment for the mark to be registered to obtain protection, to some extent. This work focuses on what constitutes a well-known mark, how they are exempt, to some extent, from the above principles and how they are regulated and protected in various legal contexts.