Ernesto Cesàro (12 March 1859 – 12 September 1906) was an Italian mathematician who worked in the field of differential geometry.

After a rather disappointing start of his academic career and a journey through Europe - with the most important stop at Liège, where his older brother Giuseppe Raimondo Pio Cesàro was teaching mineralogy at the local university - Ernesto Cesàro graduated from the University of Rome in 1887, while he was already part of the Royal Science Society of Belgium for the numerous works that he had already published.

He settled in Rome, where he stayed as a professor at the Sapienza University until his accidental death, while trying to rescue his youngest son Manlio from drowning.

Lessons of intrinsic geometry, written in 1894, explains in particular the construction of a fractal curve.

After that, Cesàro also studied the "snowflake curve" of von Koch, continuous but not differentiable in any of its points.