On December 8 and 9, 2014, the National Academies of Sciences, Engineering, and Medicine held a workshop to explore opportunities in lightweight materials for armored vehicles. This was the ninth workshop in an ongoing series for the U.S. military on materials and manufacturing issues. The workshop discussed future advances in weight reduction by materials substitution for vehicles, including such topics as armor, structure, automotive parts, and armaments. This publication summarizes the presentations and discussions from the workshop.