Xiaoliang Sunney Xie (born 1962 in Beijing, China) is the Mallinckrodt Professor of Chemistry and Chemical Biology at Harvard University. Xie is considered a founding father of single-molecule enzymology.In 1999, he became the first full professor at Harvard University from the People's Republic of China since China's reform in 1978.

Among the first to conduct fluorescence studies of single molecules at room temperature in the early 1990s, his research group has contributed to the emergence of the field of single-molecule biophysical chemistry and its application to biology. His work focuses on single-molecule enzymology, protein conformational dynamics, and the study of gene expression and regulation in living cells. His group also pioneered CARS microscopy and stimulated Raman scattering microscopy, sensitive biomedical imaging techniques that allow 3D imaging of live cells and organisms based on vibrational spectroscopy.In addition, his group have led the developments of single-cell whole genome amplification for single cell genomics.He received Albany Medical Center Prize in 2015.