Ernesto Sergent-Marceau (d. February 12, 1895) was an Italian astronomer and stellar cartographer with a particular devotion to meteorology. In 1855, he entered the Specola in Milan as a “free pupil” and within the following decade he rose in the academic ranks to become an Adjunct Astronomer in 1866. Both leading up to this appointment, and in the years following it, Sergent-Marceau worked for extended periods at the Astronomical Observatory of Brera in Milan, including in their extensive astronomical archive. In 1872, Sergent-Marceau left the Specola to teach in Bari.

Throughout his life, Sergent-Marceau was an ardent astronomer and educator. Among his professional activities, he served as editor for the publication Astronomical Ephemerides of Milan from 1857 to 1872.