Katharina Gaus (12 July 1972 – 3 March 2021) was a German-Australian immunologist and molecular microscopist. She was an NHMRC Senior Research Fellow and founding head of the Cellular Membrane Biology Lab, part of the Centre for Vascular Research at the University of New South Wales. Gaus used new super-resolution fluorescence microscopes to examine the plasma membrane within intact living cells, and study cell signalling at the level of single molecules to better understand how cells "make decisions". A key discovery of Gaus and her team was how T-cells decide to switch on the body's immune system to attack diseases. Her work is of importance to the development of drugs that can work with T-cells in support of the immune system.