Textbook in PDF format This book presents macroscopic theories of magnetoelastic interactions in solids, mainly for saturated ferromagnetoelastic materials. In these materials, the distributed magnetic moments are aligned and have a fixed magnitude. A disturbance of the magnetic moments propagates as what is called spin waves. In elastic ferromagnets, acoustic waves may interact with spin waves, which is referred to as phonon-magnon interaction. Continuum modeling of magnetoelastic interactions in saturated ferromagnets has a few unique and interesting features. In addition to the magnetic body force and couple on the magnetic moments, the short-range interaction among neighboring magnetic moments may be described by distributed surface couples. This leads to a magnetization gradient theory. The angular momenta associated with the magnetic moments need to be considered for spin waves. In addition, the saturation condition on the magnetization vector functions as a constraint mathematically, which has important implications in the constitutive relations of these materials