| Sport | Rugby union |
|---|---|
| Instituted | 1992 (as Herts/Middlesex) |
| Number of teams | 12 |
| Country |  England |
| Website | [1] |
Counties 3 Herts/Middlesex (formerly Herts/Middlesex 1) is a tier 9 English Rugby Union league. It is organised by the London and South East Division Rugby Football Union for clubs in Hertfordshire and parts of north-west London that traditionally was encompassed by the historic county of Middlesex. Promotion is to Counties 2 Herts/Middlesex relegation is to the Middlesex RFU merit leagues.
Historically the league was a level 8 league but following the RFU's Adult Competition Review, from season 2022-23 it became a level 9 competition and adopted its current name Counties 3 Herts/Middlesex.