Fiona Watt, (born 28 March 1956) is a British scientist who is internationally known for detailing the mechanisms that control epidermal stem cell renewal, differentiation, and tissue aggregation. She is also known for discovering how each of those processes' regulations are removed in diseased cells. She is director of the Centre for Stem Cells & Regenerative Medicine at Kings College London, and executive chair of the MRC.

She became the first woman president of the International Society of Stem Cell Research (ISSCR) in 2008, and has advocated on behalf of women in science. Previously she held the position of Deputy Director at the Cancer Research UK Cambridge Research Institute and the Wellcome Trust Centre for Stem Cell Research. Since 2013, she has co-led the Human Induced Pluripotent Stem Cell Initiative (HipSci). HipSci aims to the generate and characterise a large collection of human induced pluripotent stem cells, in order to discover how genomic variation affects cellular phenotype and to identify new mechanisms of disease.