This volume includes six lectures given at the ICTAC (International Colloquium on Theoretical Aspects of Computing) School on Formal Methods for an Informal World, held on September 1-7, 2021, originally scheduled to take place in Astana but held in virtual mode due to the pandemic. The school addressed the use of formal methods at various levels of rigour in different application domains: human-computer interaction, cognitive science, business process management, robotics, and healthcare. The emphasis of the school was on practical applications in which formal methods provide unambiguous descriptions of the real world that facilitate understanding and formal and informal analysis. The target audience consists of graduate students, young researchers and industrial practitioners, from both computer science and other fields that make use of computational methods.