This Practice Note considers the legal, regulatory and practical issues arising on mega projects. It explains what constitutes a mega project, distinguishes a mega project from a Nationally Significant Infrastructure Project (NSIP) in England, a Significant Infrastructure Project (SIP) in Wales and a national development in Scotland. This Practice Note considers relevant government guidance, procurement strategy, governance, risk allocation, contractual structure and dispute management. It is intended for construction lawyers advising clients involved in the planning, procurement, delivery or oversight of mega projects. Mega projects occupy a distinct place within the construction and infrastructure landscape. They are not simply large projects, but projects of exceptional scale, complexity and strategic importance, typically involving long delivery periods, multiple contracting interfaces and significant public or political scrutiny. For construction lawyers, mega projects require a shift in approach. Familiar legal principles continue to apply, but the consequences of poor drafting, weak governance, unrealistic risk allocation or inadequate regulatory planning are magnified and may become systemic. In practice, mega projects are as much about procurement strategy, risk management and