This book provides a comprehensive overview of how Ukraine has developed systems to counter disinformation amid ongoing hybrid threats. It offers practical insights into building national resilience against information warfare in a real-time war environment. The problem this book sets out to solve is how states and societies can design and implement effective, ethical, and scalable counter-disinformation systems in an era of information warfare. Drawing on Ukraine's experience since 2014, Counter Disinformation System Development in Ukraine explores the evolution of its legal frameworks, strategic communications, media literacy efforts, cybersecurity infrastructure, and public-private cooperation. These elements are examined as interconnected pillars supporting the country's broader information resilience strategy. The book maps the institutional architecture behind Ukraine's response, from government agencies and NGOs to tech platforms and civil society actors, highlighting both successful practices and persistent challenges. Key topics include the role of digital platforms and AI in identifying and countering malign narratives, the development of early warning and rapid response systems, the importance of cross-sectoral collaboration, and the critical need for democratic safeguards to prevent overreach. The book also addresses how Russia's disinformation campaigns have evolved over time, and how Ukraine's countermeasures have adapted in response. These topics are highly relevant not only for countries facing similar threats, but also for policymakers, media professionals, and researchers interested in defending democratic values in the digital age. As disinformation becomes more sophisticated and globally networked, Ukraine's case provides a real-world model for building adaptive and resilient systems under pressure. This book is intended for policy-makers, strategic communication professionals, academics, security experts, civil society leaders, and anyone engaged in the fight against disinformation in democratic societies. By presenting Ukraine's hard-earned lessons and tested practices, it offers a framework that can be adapted in other national or regional contexts.