Ultrasonic additive manufacturing (UAM) is a unique three-dimensional (3D) printing technique that employs ultrasonic waves or vibrations to generate complex, multi-layered metallic components by joining layers of metal foil or sheets. UAM is also defined as the solid-state process of joining dissimilar metals (typically challenging to weld) at relatively low temperatures. The process typically begins by fastening a metal sheet or foil between two sonotrodes. The sonotrodes are specifically designed tools used in UAM to produce complex 3D shapes from metal parts. During the UAM process, the sonotrodes undergo high-frequency vibration while moving across the metal, which softens, and bonds the metal by creating a solid-state bond between the layers. Consequently, the layers are built up layer-by-layer into the desired complex 3D shape. The critical advantage of the UAM process is that it enables the creation of highly complex geometric metal parts that are challenging when using traditional casting or machining techniques. UAM can be used to create metal parts from different metals, alloys, or materials with graded properties. In addition, UAM has the potential to produce high-performance and customized parts with minimal waste. Therefore, it can be potentially applied in highly specialized industries such as automotive, electronics, aerospace, and health/medical devices. Given its potential, UAM is currently actively researched and developed by academia, and industry worldwide. Hence, this chapter provides an overview of the UAM process, its advantages, limitations, and prospects.