The 2021 IEEE International Symposium on Radio-Frequency Integration Technology (RFIT2021) is a focused yet interdisciplinary advanced forum for microwave and microelectronics technologies. It is an annual event in region 10 solely sponsored by IEEE MTT Society. It will rotate among Taiwan, Korea, Singapore, China, and Japan, and will be held in end of August or beginning of September every year. RFIT provides a forum for the integrated circuit and technology communities to meet and present the latest developments in integrated circuit design, technology and system integration, with emphasis on wireless communication systems and emerging applications such as biology and healthcare, as well as emerging THz and 3D integration technologies. RFIT will continue to feature both invited and contributed papers.