Chalybion californicum, the common blue mud dauber of North America, is a metallic blue species of mud dauber wasp first described by Henri Louis Frédéric de Saussure in 1867.

[2] It is similar in shape and colour to the steel-blue cricket hunter (Chlorion aerarium).

It is ranged from northern Mexico to southern Canada, including most of the United States.

[4] Females can build their own nests, but often refurbish nests abandoned by other wasps and bees,[4] particularly those of Sceliphron caementarium,[5] removing any spiders captured by S. caementarium and the larva, replacing it with an egg of its own and freshly caught spiders.

They pollinate some common wildflowers, including Berberis vulgaris, Daucus carota, and Zizia aurea.