| O'Connell | J | | Volunteer from America (Irish) serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| O'Hara | Hubert | | Chicago Corps
Volunteer from America (Irish) serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| O'Hara | Michael C | | Chicago Corps. Died Dalmanutha 23-27 /08/1900
Volunteer from America (Irish) serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| O'Haughey | James | | Volunteer from America (Irish) serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| O'Kelly | Q | | Volunteer from America serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| O'Shea | Michael John | | Volunteer from America (Irish) serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| Oates | P J | Captain | Volunteer from America (Irish) serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| Oates | Tommy | | Died Modderspruit & Nicholsonsnek
Volunteer from America (Irish) serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | American volunteers |
| Ockerse | T | | Volunteer from Holland / Belgium serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Belgian and Dutch volunteers |
| Odman | Andrew John | | Volunteer from Sweden serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Scandinavian volunteers |
| Oelke | G | | Volunteer from Germany serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | German volunteers |
| Oertel | Curt | | Volunteer from Germany serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | German volunteers |
| Offingra | W | | Volunteer from Holland / Belgium serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Belgian and Dutch volunteers |
| Ogterop | Cornelis | | Volunteer from Holland / Belgium serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Belgian and Dutch volunteers |
| Ohlson | Charles | | Volunteer from Sweden serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Scandinavian volunteers |
| Ohlsson | John Martin | | Returned March 1900
Volunteer from Sweden serving with the Boer forces
Source: Hjaltarna vid Magersfontein, Kapten H E Uddgren, Sweden, 1924 | Scandinavian volunteers |
| Ohlsson | John Martin | | Volunteer from Sweden serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Scandinavian volunteers |
| Olesen | Frede | | KIA 11/12/1899
Volunteer from Denmark serving with the Boer forces
Source: Hjaltarna vid Magersfontein, Kapten H E Uddgren, Sweden, 1924 | Scandinavian volunteers |
| Oleson | Frede | | Died Magersfontein 11/12/1899
Volunteer from Denmark serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Scandinavian volunteers |
| Olie | Cornelius (Jr) | | Volunteer from Holland / Belgium serving with the Boer forces
Source: Anglo Boer War Museum database, August 2016 | Belgian and Dutch volunteers |
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