| Li Rui | |
| Birth Date: | 8 December 1768 |
| Birth Place: | Suzhou, China |
| Death Place: | Suzhou, China |
| Nationality: | Chinese |
| Fields: | Mathematics |
| Known For: | Descartes' rule of signs |
Li Rui (; 8 December 1768 in Suzhou – 30 June 1817 in Suzhou) was a Chinese mathematician. Li discovered independently an equivalent version of what is known today as Descartes' rule of signs.