Thesetransactions publish research in computer-based methods of computationalcollective intelligence (CCI) and their applications in a wide range of fieldssuch as the semantic Web, social networks, and multi-agent systems. TCCIstrives to cover new methodological, theoretical and practical aspects of CCIunderstood as the form of intelligence that emerges from the collaboration andcompetition of many individuals (artificial and/or natural). The application ofmultiple computational intelligence technologies, such as fuzzy systems,evolutionary computation, neural systems, consensus theory, etc., aims tosupport human and other collective intelligence and to create new forms of CCIin natural and/or artificial systems. This twenty-first issue contains 7 carefullyselected and revised contributions.