Abstract: Disclosed herein is a modular process plant structural system which includes numerous modules, all ISO-certified under ISO 1496 and capable of holding within the entire module at least one chemical (or non-chemical) production plant piece of equipment, capable of individually being shipped or transported. The modules can be stacked vertically, horizontally, or mixed (both vertical and horizontal arrangement). The modules are pre-fabricated offsite, built with the desired equipment within the module, pre-plumbed with piping, instrumentation, and electrical wiring, and then the multiple modules are shipped multimodally as ISO 1496 containers to the desired location and assembled to form a plant. Generally, two or more modules are connected together to form a complete plant. The plant can be of any type, e.g., chemical, mechanical/production, thermal, and the like, or of any size, e.g., production, small, micro, or pilot plant scale.