St. Seiriol
| Name | St. Seiriol |
| Type | Auxiliary minesweeper |
| GRT | 928 tons |
| Country |  British |
| Built | 1914 |
| Builder | A. & J. Inglis, Ltd., Glasgow |
| Operator | Royal Navy |
| History | Peace-time operator: Liverpool & North Wales SS. Co., Liverpool |
U-boat attacks on Auxiliary minesweeper St. Seiriol
| Date | U-boat | Loss type | Position | Location | Route | Cargo | Casualties | |
| 1 | 25 Apr 1918 | UC 4 (Ernst Berlin) | Sunk | Mined off the Shipwash LV | 12 |
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