Counties 3 Hampshire (formerly Hampshire 1) is an English level 9 Rugby Union league for teams based in Hampshire and the Isle of Wight. Up until the 2017–18 season it was known as Hampshire 2 but was changed to Hampshire 1 following the restructuring of the Hampshire leagues, which would see the re-introduction of a third division as well as 2nd and 3rd XV sides joining for the first time. Following the RFU's Adult Competition Review, from season 2022–23 it adopted its current name Counties 3 Hampshire.

Each year some of the clubs in this division also take part in the RFU Junior Vase - a level 9-12 national competition.

Promoted teams move up to Counties 2 Hampshire. Relegated teams drop down to Counties 4 Hampshire.

The points system is as follows.

No team can get more than 5 points in a match. Points awarded are the same regardless of the outcome at home or away.

Departing were Andover II, Romsey and Southampton, all to Counties 2 Hampshire.

Farnham III were initially placed in the league with Overton (9th) having been relegated to Counties 4 Hampshire. However, shortly before the season began Overton were reinstated in the higher league with Farnham III taking their place in Counties 4 Hampshire.

Eastleigh II (7th in 2024-25) began the campaign but subsequently withdrew in November leaving nine clubs to contest the outstanding fixtures.