This chapter explores the ultrasonic additive manufacturing (UAM) process. This process is an advanced, solid-state, metal additive/subtractive hybrid manufacturing process. The process combines high-power ultrasonic welding and computer numerical control milling to fabricate solid metal components, layer by layer, from metal foils. The chapter discusses the process fundamentals and three key abilities of UAM: complicated geometries, dissimilar material bonding, and object embedment. Combining these three key abilities positions UAM as a unique and attractive method to create metal matrix–based freeform multifunctional structures for high-value engineering applications. © 2023 Elsevier Ltd. All rights reserved.