This document provides an overview of citric acid production. It discusses the history of citric acid's discovery and initial industrial production. Microbes like Aspergillus niger are used in fermentation to produce citric acid from sugars. Three main fermentation techniques are described: surface, submerged, and solid state fermentation. Key factors that affect citric acid production are also outlined. Industrial production meets most global demand, and citric acid has many applications in food/beverages, pharmaceuticals, household cleaners, and more. The largest global producers are also listed.