There are 7 13-letter words that end with 'ium'.
| armamentarium | decamethonium |
| hexamethonium | mycobacterium |
| rutherfordium | perichondrium |
| zoosporangium | |
Note: These 7 13-letter words that end with 'ium' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words end with rium, nium, dium, lium, cium, tium, gium, mium, bium, sium, vium, hium, pium, uium, xium, zium.
5-letter words end with 'ium' (4)