Note: You are currently viewing documentation for Moodle 3.2. Up-to-date documentation for the latest stable version of Moodle is probably available here: Site administrators.
Site administrators have permissions to do anything.
Users may be assigned the role of site administrator by another site administrator in Settings > Site administration > Users > Permissions > Site administrators, but the role itself cannot be edited (or deleted!).
Note: The primary administrator (created when the site was created) cannot be removed from the site administrator role.