The International Conference Declarative AI 2020 brings together RuleML+RR, DecisionCAMP, and Reasoning Web Summer School. It will take place in Oslo, Norway, on 23 June – 1 July, 2020. The event aims at presenting the latest advancements in AI and Rules, Reasoning, Decisions, and Explanations and their adoption in IT systems towards improving key fields such as environment, health and societies.