Producing hydrogen using ultrasonic waves offers tremendous opportunities, which could lead to a clean, affordable and reliable energy source. Introducing high-frequency ultrasonic waves to liquid water could provide an efficient way to produce efficient and clean hydrogen. This particular review makes a focus on the application of power ultrasound in hydrogen production and discusses the challenges, opportunities and future directions. This new, ultrasonic based hydrogen production technology is given the name of "Sono-Hydro-Gen". It is well known that hydrogen can be formed from the dissociation of water molecules subjected to ultrasound via the so-called sonolysis process. Factors affecting the hydrogen production rate and the theory beyond these effects are described herein. The average hydrogen production-rate reported from the Sono-Hydro-Gen process is 0.8 mu mol per minute at an acoustic intensity of 0.6 W cm(-2). This review also compares the Sono-HydroGen technology with the most commonly used technologies and it is found that this technology could lead to a prosperous and secure hydrogen energy for the future. Recent numerical and experimental investigations on the hydrogen production pathways have been reviewed showing various numerical simulations for different experimental configurations. Finally, performance and efficiency criteria are discussed along with the challenges associated with the Sono-Hydro-Gen process. Crown Copyright (C) 2019 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. All rights reserved.