Middlesex 3 was an English level 12 Rugby Union league with teams from north-west London taking part. Promoted teams moved up to Middlesex 2 and relegation was to Middlesex 4. The division was cancelled at the end of the 1995–96 campaign after nine seasons due to the merger of the Hertfordshire and Middlesex regional leagues.
Original teams
When league rugby began in 1987 this division was split into two regional leagues containing the following teams:
The original Middlesex 3 was a tier 10 league, split into two regional divisions (north and south). Promotion was up to Middlesex 2 and there was no relegation.
The creation of Middlesex 4 ahead of the 1988–89 season saw Middlesex 3 merged into a single division remaining at tier 10 of the league structure. Promotion continued to Middlesex 2, while relegation was to the new Middlesex 4.
The creation of Herts/Middlesex at the beginning of the 1992–93 season meant that Middlesex 3 dropped to become a tier 11 league. The introduction of National 5 South for the 1993–94 season meant that Middlesex 3 dropped another level to become a tier 12 league for the years that National 5 South was active. Promotion and relegation continued to Middlesex 2 and Middlesex 4 respectively. The merging of the Hertfordshire and Middlesex regional divisions at the end of the 1995–96 season meant that Middlesex 3 was cancelled.
^Champions Roxeth Manor Old Boys were promoted two levels up into Middlesex 1 due to restructuring as a result of the introduction of the new Herts/Middlesex division for the following season.
^Runners up Wembley were also promoted two levels up into Middlesex 1. Teams ranked 3rd to 11th were promoted into Middlesex 2 as part of the league restructuring.
^Due to restructuring of the Herfordshire and Middlesex leagues there was no relegation this season.
^Hammersmith & Fulham's title was Middlesex 3 South.
