Sandra Diane Knapp FLS FRS (born 1956) is an American-born botanist. She is a merit researcher of the Plants Division of the Natural History Museum, London and from 2018 was the president of the Linnean Society of London. While working at the Natural History Museum, London she has overseen the Flora Mesoamericana inventory of Central American plants. She has published several books on botanical subjects as well as a significant number of scientific articles. In 2016 she was awarded the Linnean Medal. In 2022 she was elected as a Fellow of the Royal Society.