寻水兽（英文：Afanc），又称为阿凡克，是欧洲神话中的一只大水怪。

寻水兽是一个生活在康威河亚·阿凡克池沼的怪兽，体形非常强壮巨大，外型很像海狸，而且奔跑速度相当快，喜欢生活在水里。它能制造水灾或散发瘟疫，所以民众便采取措施消灭寻水兽，但人类的普通武器却伤不了它分毫。

寻水兽是古老魔法的产物，传说中寻水兽是由强力魔法从泥土中生出来的怪物，只要被寻水兽所伤的人类都将必死无疑。

The Afanc (Welsh pronunciation: [ˈavank], sometimes also called Addanc, [ˈaðank]) is a lake monster from Welsh mythology. Its exact description varies; it is described variously as resembling a crocodile, beaver or dwarf-like creature, and is sometimes said to be a demon. The lake in which it dwells also varies; it is variously said to live in Llyn Llion, Llyn Barfog, near Brynberian Bridge or in Llyn yr Afanc, a lake near Betws-y-Coed that was named after the creature.