Eustachy Karol Żyliński (19 September 1889 – 4 July 1954) was a Polish mathematician and university professor known for his work on number theory, algebra, and logic.

From 1918, as an associate professor, he lectured at the Polish University College and the Higher Technical Institute in Kiev.

1929 he was dean of the Faculty of Mathematics and Natural Sciences of the Jagiellonian University and was the promoter of Władysław Orlicz's doctoral dissertation.

At that time, he worked at the Ministry of Foreign Affairs, and was also nominated as consul general in Kiev, but did not assume this office.

[7] In 1947 he moved to Gliwice, where in the years 1946–1951 he was the head of the Department of Mathematics at the Faculty of Engineering and Construction of the Silesian University of Technology.