Ydroussa (Greek: Υδρούσα, before 1927: Κάτω Κόττορι – Kato Kottori)[2] is a village in Florina regional unit, Western Macedonia, Greece.

[3] In statistics gathered by Vasil Kanchov in 1900, Kato Kottori was populated by 174 Christian Albanians and 600 Bulgarians.

[4] Kanchov wrote that Christian Albanians of the late Ottoman period in Kato Kottori were increasingly being assimilated by its Bulgarian population.

[8] In fieldwork done by anthropologist Riki Van Boeschoten in late 1993, (Kato) Ydroussa was populated by Slavophones and Arvanites.

[8] In the late 1990s, in fieldwork done by Ioannis Manos, much of the Ydroussa village population self identified as Dopioi, a designation used by Slavophones of the Florina region and the remainder as Arvanites.