A rotating shaft and a method for additively manufacturing the rotating shaft are provided. The rotating shaft includes an elongated body extending along an axial direction and including an inner surface that defines a hollow central portion. An internal support structure extends from the inner surface into the hollow central portion to stiffen the rotating shaft and provide a high stiffness-to-weight ratio. The internal support structures may include stiffening ribs, truss structures, mesh structures, solid disks, and/or regions having a decreased density relative to the elongated body. The elongated body and some or all internal features may be integrally formed as a single monolithic component.