This paper presents a new model of megaproject motives called the ABC model (altruism, benefit, and common good) of megaproject motives drawn from 13 examples of megaprojects. The purpose of this research was to understand what drives megaprojects as existing models fit infrastructure projects but not megaprojects that are driven by compassion, such as the Exxon Valdez clean up. Existing models such as the four sublimes also mistake vested interests for project motives. The ABC model benefits science in the discrimination, selection, and evaluation of megaprojects. This model extends into the resource allocation, staffing, and tolerance of soft factors where required in terms of variances in budget, time, and outcome.