| Johann Friedrich Hennert | |
| Birth Date: | 19 October 1733 |
| Birth Place: | Berlin, Prussia |
| Death Place: | Utrecht |
| Nationality: | German |
| Fields: | Mathematics Physics |
| Workplaces: | University of Utrecht |
| Doctoral Advisor: | Leonhard Euler Joseph-Nicolas Delisle |
| Doctoral Students: | Jean Henri van Swinden |
Johann Friedrich Hennert (19 October 1733 – 30 March 1813) was German-born and lectured in mathematics and physics at the University of Utrecht. He was a significant student of Leonhard Euler. He was known for his inclination towards the British school of philosophy.
Hennert held the chair of mathematics at the University of Utrecht until 1805.
Hennert was an important figure in the history of Dutch mathematics. He wrote a number of textbooks on differential calculus.Jean Henri van Swinden was one of his most important students.