oxonium ions

https://doi.org/10.1351/goldbook.O04378
The parent ion H3O+ and substitution derivatives thereof.
See:
onium compounds
Source:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1355 [Terms] [Paper]