The blue orchard bee (Osmia lignaria), also known as the orchard mason bee, mason bee, orchard bee, and Osmia bee, is named for its shiny blue coloration and the fact that it pollinates orchard crops. These bees are native to North America and are found throughout most of the United States. However, this bee is not established in the deep south and is rare in the Great Plains.

The blue orchard bee is slightly smaller than a honey bee; males are approximately 11 to 12 mm and females are approximately 14 mm in length. They are a shiny dark blue color. Males have longer antennae and an additional tuft of light colored hair on their faces than females. Females have hairs on the underside of their abdomens adapted for carrying pollen.