Here's the scientific classification of an earthworm, starting with the broadest category and going down to the species:

* Domain: Eukarya (organisms with cells containing a nucleus)

* Kingdom: Animalia (multicellular organisms that obtain nutrition by consuming other organisms)

* Phylum: Annelida (segmented worms)

* Class: Clitellata (earthworms and leeches)

* Order: Haplotaxida (earthworms)

* Family: Lumbricidae (common earthworms)

* Genus: *Lumbricus* (common earthworms)

* Species: *Lumbricus terrestris* (common earthworm)

Note: There are many different species of earthworms, so the specific species will vary depending on the particular earthworm you are looking at. *Lumbricus terrestris* is just one common example.