<p>Elastic properties are important characteristics for design purposes. Among various techniques, in recent years, ultrasound phase spectroscopy (UPS) has emerged as a more reliable technique than the conventional pulse-echo technique in studying the elastic properties of a wide range of complex multiphase materials. In UPS, continuous, harmonic, and sinusoidal ultrasonic waves are passed through a sample over a broad frequency range, and the ultrasonic velocity is determined using the phase shift versus frequency plot. Measurements are also possible along different directions in cuboid samples, allowing the study of anisotropic materials. In this maiden review of the UPS technique, a detailed discussion of the theoretical background, along with an analysis of the advantages and disadvantages of the UPS technique with respect to other methods of elastic property measurement, is provided. Subsequently, a critical analysis of the measurements performed using the UPS technique in different categories of materials has been discussed.</p>