| Giolladhe | A servant of the holy God. |
| GIynna | A graceful, pure woman |
| Gizane | christs incarnation |
| Glaleanna | Dwells in the glen |
| Glen | Dweller of Valley; Derived from the Gaelic 'gleana', meaning valley. Used both as a surname and given name. Famous bearer: American singer Glen Campbell.; From the glen. Valley.; A Secluded, Woody Valley; From the secluded narrow valley; From the valley |
| Glenna | A name meaning from the valley floor. |
| Gliona | From the Greek Cleone daughter of a river god |
| Glynna | A name meaning from the valley. |
| Gobinet | Irish form of Abigail bringsjoy |
| Gobnait | Irish form of Abigail bringsjoy |
| Gobnat | Irish form of Abigail bringsjoy |
| Gofraidh | Peace of the God or Gods peace |
| Gogarty | Descendant of the proud warrior |
| Golligan | A descendant of the bright one. |
| Gormain | A name meaning noble or dignified |
| Gorman | One who is a small blueeyed man |
| Gormghlaith | A name meaning noble princess |
| Gormley | One from the dark meadow lands |
| Gormly | Derived from a bluecolored hill. |
| Gorrie | A variant of the name Gordon. |
| Gorry | A diminutive of the name Gordon. |
| Gothfraidh | A name meaning peace of the God. |
| Gough | Derived from the word red. |
| Grady | A person of noble descent. |
| Granuaile | Grace of the sea or ocean |
| Greagoir | The Gaelic form of the name Gregory. |
| Griffin | Fierce; Having a hooked nose; Mythological Beast; Strong in faith.; Surname. |
| Grioghar | A vigilant and watchful person. |
| Gryffyn | mythological beast |
| Gubnat | Irish form of Abigail bringsjoy |
| Gwenhyvar | A fair and soft white phantom. |
| Hagan | A descendant of the little fire. |
| Hanlon | A descendant of a champion. |
| Hanraoi | The Irish form of the name Henry. |
| Harken | To listen or pay attention. |
| Harrington | From the town of the hares estate. |
| Heddwyn | A fair and blessed peacemaker. |
| Hegarty | Descendant of the horse rider |
| Heledd | a traditional name |
| Hennessy | Descendant of the proud one. |