Eudialyte, whose name derives from the Greek phrase Εὖ διάλυτος, eu dialytos, meaning "well decomposable", is a somewhat rare, nine-member-ring cyclosilicate mineral, which forms in alkaline igneous rocks, such as nepheline syenites.

Eudialyte typically has a significant content of U, Pb, Nb, Ta, Zr, Hf, and rare earth elements (REE).

Associate minerals include: microcline, nepheline, aegirine, lamprophyllite, lorenzenite, catapleiite, murmanite, arfvedsonite, sodalite, aenigmatite, rinkite, låvenite, titanite and titanian magnetite.

Prominent localities of eudialyte include Mont Saint-Hilaire in Canada, Kola Peninsula in Russia and Poços de Caldas in Brazil, but it is also found in Greenland, Norway, and Arkansas.

The group includes Zr−, OH−, Cl−, F−, CO3− and possibly also SO4-bearing silicates of Na, K, H3O, Ca, Sr, REEs, Mn, Fe, Nb and W. Electron vacancies can be present in their structure, too.