"Resources to validate new sanitation technologies and prepare for market entry – prerequisites for achieving sustainable, scaled solutions – tend to be quite scarce compared to those available to scale proven solutions. As such, a problematic ‘Pioneer Gap’ exists. This funder landscape seeks to both clarify the ‘Pioneer Gap’ and point readers to potential funding and other resources poised to help fill this problematic gap. Two promising forms of funding are explored in detail: catalytic philanthropy and blended finance leveraging impact investment."