Lean Construction Ireland (LCi) is a community of learning and practice that advocates for the transformation of the Irish construction sector through the adoption of Lean thinking and practices by the entire sector to enable and sustain enhanced effectiveness, efficiency, productivity, and profitability for all stakeholders in the value chain. A core LCi principle is the open exchange of Lean knowledge, information, and experiences to enable the individual, organisational, and sectoral transformation journeys. So, it is with great pleasure that Lean Construction Ireland launches the fourth publication of its Annual Book of Cases – the key Lean Construction reference publication for the Irish construction sector, from Clients and Owners to Professional Services Providers, Contractors, Sub-Contractors, Suppliers, Consultants, and Academia. The Book provides real-world, practical, and accessible examples of Irish Construction organisations implementing Lean thinking and practices. Each case provides the context for the Lean initiative; details the Lean thinking, tools, and techniques applied on the initiative; and describes the impact and benefits of the initiative. These cases clearly demonstrate that the Irish construction sector is beginning to normalise the application of Lean thinking and practices for the design and delivery of capital projects as well as for internal operational excellence purposes.