并非下表中的所有实体都能在所有的浏览器中正确地显示。
目前，IE 11 是唯一一个能正确显示所有 HTML5 实体的浏览器。
| 字符 | 实体名称 | 十六进制 |
|---|---|---|
| 'O | Oacute | 000D3 |
| ó | oacute | 000F3 |
| oast | 0229B | |
| ocir | 0229A | |
| ^O | Ocirc | 000D4 |
| ^o | ocirc | 000F4 |
| О | Ocy | 0041E |
| о | ocy | 0043E |
| odash | 0229D | |
| "O | Odblac | 00150 |
| "o | odblac | 00151 |
| odiv | 02A38 | |
| ⊙ | odot | 02299 |
| odsold | 029BC | |
| OE | OElig | 00152 |
| oe | oelig | 00153 |
| ofcir | 029BF | |
| ? | Ofr | 1D512 |
| ? | ofr | 1D52C |
| ogon | 002DB | |
| `O | Ograve | 000D2 |
| ò | ograve | 000F2 |
| ogt | 029C1 | |
| ohbar | 029B5 | |
| Ω | ohm | 003A9 |
| ∮ | oint | 0222E |
| olarr | 021BA | |
| olcir | 029BE | |
| olcross | 029BB | |
| oline | 0203E | |
| olt | 029C0 | |
| O | Omacr | 0014C |
| ō | omacr | 0014D |
| Ω | Omega | 003A9 |
| ω | omega | 003C9 |
| Ο | Omicron | 0039F |
| ο | omicron | 003BF |
| omid | 029B6 | |
| ominus | 02296 | |
| ? | Oopf | 1D546 |
| ? | oopf | 1D560 |
| opar | 029B7 | |
| “ | OpenCurlyDoubleQuote | 0201C |
| ‘ | OpenCurlyQuote | 02018 |
| operp | 029B9 | |
| ⊕ | oplus | 02295 |
| Or | 02A54 | |
| ∨ | or | 02228 |
| orarr | 021BB | |
| ord | 02A5D | |
| o | order | 02134 |
| o | orderof | 02134 |
| a | ordf | 000AA |
| o | ordm | 000BA |
| origof | 022B6 | |
| oror | 02A56 | |
| orslope | 02A57 | |
| orv | 02A5B | |
| (S) | oS | 024C8 |
| ? | Oscr | 1D4AA |
| o | oscr | 02134 |
| O | Oslash | 000D8 |
| o | oslash | 000F8 |
| osol | 02298 | |
| ~O | Otilde | 000D5 |
| ~o | otilde | 000F5 |
| Otimes | 02A37 | |
| otimes | 02297 | |
| otimesas | 02A36 | |
| "O | Ouml | 000D6 |
| "o | ouml | 000F6 |
| ovbar | 0233D | |
| OverBar | 0203E | |
| OverBrace | 023DE | |
| OverBracket | 023B4 | |
| OverParenthesis | 023DC |
