| GWR 3001 Achilles Class | |
| Powertype: | Steam |
| Designer: | William Dean |
| Builder: | GWR Swindon Works |
| Builddate: | 1891–1892 |
| Ordernumber: | Lots 84, 86 |
| Serialnumber: | 1221–1240, 1261–1270 |
| Totalproduction: | 30 |
| Whytetype: | 2-2-2 |
| Uicclass: | 1A1 n2 |
| Gauge: | (Nos. 3021–3028) |
| Driverdiameter: | 7feet |
| Trailingdiameter: | 4feet |
| Operator: | Great Western Railway |
| Fleetnumbers: | 3001–3030 |
| Withdrawndate: | 1893–1894 |
| Numinclass: | 30 |
| Disposition: | All converted to 3031 Class |
The 3001 Class as constructed by William Dean at the Swindon Works of the Great Western Railway in 1891-2 was the culmination of the tradition of GWR 2-2-2 locomotives that had begun with Gooch's North Star over 50 years earlier. The 3001s, which had 7feet driving wheels, were built in two batches:
| 1892 | 20 | 84 | 1221–1240 | 3001–3020 | align=left | ||
| 1891 | 10 | 86 | 1261–1270 | 3021–3030 | align=left | 3021–3028 built as broad-gauge convertibles |
Because of the restricted width available between the large driving wheels, these locomotives were fitted with narrow 4inchesft3inchesin (ftin) diameter boilers. In order to increase the heating surface the boilers were made longer than previous types, and were fitted with raised fireboxes. Despite the fact that the broad gauge was in its very final months, new broad gauge engines were still needed to maintain services, and eight of these new engines, Nos. 3021-3028, were built (as "convertibles") with the wheels outside the frames, to run on the broad gauge. They were duly converted to "narrow" (standard) gauge in summer 1892.
These engines were too heavy at the front end, and after a derailment in 1893 it was decided to give them front bogies. Thus transformed, in 1894 the class joined the 3031 Class, considered one of the most elegant of the entire late Victorian era.