The International Society for the Systems Sciences (ISSS) produces a Special Issue of the Systems Research and Behavioural Science (SRBS) each year, also called the ISSS Yearbook. Conceived in 1954, the ISSS is one of the first and oldest professional organisations whose members are devoted to the interdisciplinary and broadly inclusive inquiry into the nature of complex systems. 1 This Special Issue of SRBS is the ISSS Yearbook for 2021.As a member of the ISSS since 2011 and its Board of Directors since 2013, it was a privilege to be President during one of the Society's most challenging periods. The activities and outputs of the Society's academics, researchers and practitioners demonstrate an inspiring, passionate, and collective desire to improve the state of humanity and its environment. Reviewing past yearbooks, there are recurring themes of transdisciplinarity, transcending boundaries and connection through systems thinking, science and practice to improve how we might work together to solve problems and create a better future (