Eidolon Software is a company that creates software for NeXT's NeXTSTEP and OPENSTEP operating systems, as well as Apple Computer's Mac OS X.
Eidolon Software is most commonly known in the NeXTSTEP/OPENSTEP community for its PopOver E-mail client software.
Eidolon Software's name is inspired from the meaning of eidolon meaning "ideal" or "ghost" (etymology from Greek for image).