Today science plays an important role in many sectors and spheres of human life. The progress in science serves as one of the main indicators of the development of a society, as well as that of the individual states. If analysing all scientific trends, two global scientific currents can be seen—natural science and social science. This division of the sciences historically led to the formation of two global international councils in the twentieth century. The world has changed significantly over the past 100 years. The global problems of humankind are so complex that for any science domain it is simply impossible to solve them in isolation. High speed of decision-making, evaluation of social and physical consequences, and a systematic and comprehensive approach to information processing are important features of solving global problems. These trends initiated the process of merging of the two major international scientific unions, ICS and ISSC. Over the decade 2005–2015, ICS and ISSC worked increasingly closely together. The International Science Council (ISC) was created in 2018 from a merger of the two international councils. This merger is the reflection of the objective need for the world science community to unite for the sake of solving global problems. This chapter focuses on the motivations for the merger of the two councils, and on the main aspects of the process.