A Twist-interlocking Engine Housing and Air Filter System and Method is disclosed. The filter assembly provides unequaled ease of installation and removal, as well as superior sealing between the housing and the filter assembly. For installation, the user needs only to insert the filter into the housing and then give the filter assembly a one-quarter turn or less to lock the filter assembly into the housing. There are features within the filter base that snap-locks the filter in place to resist inadvertent loosening. Finally, the housing and filter are designed so that the outer flange of the filter base is recessed into the side of the housing in order to prevent the intrusion of unwanted grime and/or fluids.