The Hero Pledge initiative is a public engagement initiative of the Heroic Imagination Project, a nonprofit organization in San Francisco, CA that works to create more heroic action in the world. The initiative consists of a web-based pledge to act heroically and a 4-week course that develops heroic abilities in its participants. The pledge calls web visitors to identify as future heroes and commit to developing their ability to respond on behalf of others, for a moral cause, and without the expectation of personal gain. The course builds the knowledge, emotional skills, social skills, and habits that the organization believes are necessary for heroic action based on the research of its founder, Dr. Philip Zimbardo, and others. This document outlines the initiative, its approach to behavior change, its theoretical underpinnings in positive psychology, and its evaluation plan. If it has been well-constructed, the Hero Pledge initiative should measurably increase the incidence of heroic acts in its participants.