Bertmainius monachus
{{Short description|Species of spider}}
{{Speciesbox
| taxon = Bertmainius monachus
| authority = Main, Rix & Cooper, 2015
}}
Bertmainius monachus is a spider in the family Migidae. It was first described in 2015 by Mark Harvey, Barbara York Main, Michael Rix and Steven Cooper, and is endemic to south-western Australia.