We present our contractualist theory of intergenerational justice. We begin by describing obstacles that all approaches must overcome in addressing intergenerational justice, including the non-identity problem, the unidirectional time problem, and uncertainty. We also consider one of the chief problems in the intergenerational justice literature: defining the term, “generations.” Without a clear definition of the term, there can be no solid foundation upon which to build principles of intergenerational justice. Therefore, we proceed to explicitly state and defend our definition of generations: age cohorts that each span twenty years. Further, at any given time, approximately five generations exist concurrently with each other. After explaining this definition and its implications, we move on to the creation of a Rawlsian original position that includes multiple generations, reflecting the concurrency of generations that reflects reality. We then argue that agents in the original position, as we have modified it, will select a principle of intergenerational justice that springs from the same rationale that undergirds Fair Equality of Opportunity. We therefore refer to our principle as Intergenerational Fair Equality of Opportunity (IFEO).