Green hydrogen, produced from renewable energy sources (e.g., by electrolysis), is projected to play a pivotal role in the defossilization of a wide range of applications. Water is a fundamental component of this process, as hydrogen (H2) production via electrolysis requires water (H2O) as a raw material to be split into hydrogen and oxygen. However, freshwater is a scarce resource in many regions of the world, and densely populated areas are increasingly experiencing water scarcity. This trend is likely to be exacerbated by ongoing climate change and global population growth. From an economic perspective, sunny and dry regions of the planet seem particularly suitable for hydrogen production due to their abundant solar energy. However, water availability for hydrogen production depends on more than just physical supply; factors such as water quality, the regeneration of water reserves, and local social and environmental impacts of water withdrawal must also be considered. Therefore, this article examines the availability of water for green hydrogen production across various regions of the world.