This chapter covers the key activities leading to 5G specification finalization in the International Telecommunication Union (ITU), Next Generation Mobile Network (NGMN), and 3rd generation partnership project. In early 2012, by taking into account 5G research activities around the world, ITU initiated studies on the development of “International Mobile Telecommunications (IMT) for 2020 and beyond,” called “IMT-2020.” The chapter explains the vision of IMT-2020 and the development of IMT-2020 radio interface technologies by ITU in relation to the international standardization of 5G. The NGMN Alliance is an industry organization of leading worldwide telecom operators, vendors, and research institutes. Founded in 2006 by international telecom operators, its objective is to ensure that the functionality and performance of NGMN infrastructure, service platforms, and devices will meet the requirements of operators and, ultimately, will satisfy end user demand and expectations.