Soybean rust is a fungal pathogen typically caused by Phakopsora pachyrhizi. It can be caused by Phakopsora meibomiae, but this is normally a weaker pathogen of the two. The disease has been reported across Asia, Australia, Africa, South America and the United States.

Soybean rust spreads via airborne spores which land on soybean leaves and germinate. The fungus can spread rapidly within a field, causing severe defoliation and yield losses. To date, soybean rust has been of economic importance in the southern United States. Signs of soybean rust have been confirmed in the Midwest, but economic losses have not occurred from this fungus.