In this context, the author discusses the definitions on secularism, secularization and secularism. This discussion will begin with the definition of these three terms as some sociologists have defined. In the next subchapter, the author will discuss the most important elements of secularism. These elements are made up of three main things that are generally related to the nature of politics, politics, and religious values. In the following section, the author will discuss the process of secularization that takes place specifically in politics. In the first and second sub-chapters, the discussion is still about secularism as a general phenomenon, therefore, in this last sub-chapter, the author attempts to narrow the scope of the discussion to political secularization only. The author will discuss four key elements of political secularization and lay it as a theoretical foundation in this thesis study. In the end, the author will briefly discuss political secularization in Indonesia.