DataMod 2021 aims at bringing together practitioners and researchers from academia, industry and research institutions interested in the combined application of computational modelling methods with data-driven techniques from the areas of knowledge management, data mining and machine learning. Modelling methodologies of interest include automata, agents, Petri nets, process algebras and rewriting systems. Application domains include social systems, ecology, biology, medicine, smart cities, governance, security, education, software engineering, and any other field that deals with complex systems and large amounts of data. Papers can present research results in any of the themes of interest for the symposium as well as application experiences, tools and promising preliminary ideas. Papers dealing with synergistic approaches that integrate modelling and knowledge management/discovery or that exploit knowledge management/discovery to develop/syntesise system models are especially welcome. Modelling and analysis methodologies include - Agent-based Methodologies - Automata-based Methodologies - Big Data Analytics - Cellular Automata - Classification - Clustering, Segmentation and Profiling - Conformance Analysis - Constraint Programming - Data Mining - Differential Equations -Game Theory - Machine Learning - Membrane Systems - Network Theory and Analysis - Ontologies - Optimisation Modelling - Petri Nets - Process Calculi - Process Mining - Rewriting Systems - Spatio-temporal Data Analysis/Mining - Statistical Model Checking - Text Mining - Topological Data Analysis Application domains include: - Biology - Brain Data and Simulation - Business Process Management - Climate Change - Cybersecurity - Ecology - Education - Environmental Risk Assessment and Management - Enterprise Architectures - Epidemiology - Genetics and Genomics - Governance - HCI and Human Behaviour - Open Source Software Development and Communities - Pharmacology - Resilience Engineering - Safety and Security Risk Assessment - Social Good - Social Software Engineering - Social Systems - Sustainable Development - Threat modelling and analysis - Urban Ecology - Smart Cities and Smart Lands