Youth, Peace, and Security Act of 2021 This bill requires the Department of State to coordinate the development and implementation of a whole-of-government strategy to promote the inclusive and meaningful participation of youth in peace building and conflict prevention, management, and resolution, as well as post-conflict and recovery efforts. The President must appoint a coordinator who, in addition to being responsible for leading the implementation of such strategy, is authorized to provide grants, emergency assistance, and technical assistance to eligible youth-led civil society organizations and youth peace-building implementers. The bill also authorizes the President to provide development assistance to expand training, technical assistance, and grants managed and controlled by youth leaders.