| Bands by Letter: | O |
| O.A.R. | – | Oberhofer | – | Of Gentlemen & Cowards | – | Of Monsters and Men |
| Oh Mercy | – | Oh My! | – | Oh Pep! | – | Oh Wonder |
| OK Go | – | Old Man Canyon | – | Old Sea Brigade | – | Old Wave |
| Olly Murs | – | OneRepublic | – | Only Seven Left | – | Opus Orange |
| Oques Grasses | – | Orphan Colours | – | Otherkin | – | Ottawa |
| Oxen | – | Oxford & Co. | – | – | – | – |
 |
 |
 |
 |
 |
