Dame Rotha Geraldine Diane Johnston, DBE (born August 1959) is a Northern Irish entrepreneur in commerce and property. Johnston is chair of Northern Ireland Screen, a non-executive director of Northern Ireland Electricity and an independent board member of the Department of Justice and Belfast Harbour Commissioners. Johnston, a native of West Belfast who attended St Dominic's Grammar School, is a non-executive Director of Allied Irish Bank and Deputy Chair of Invest Northern Ireland. She is a non-executive member of the Northern Ireland Office and Pro Chancellor at Queen's University Belfast.