Northern League One is a semi-professional soccer competition in Northern New South Wales. The competition is conducted by Northern NSW Football, one of two organising bodies in New South Wales (the other being the National Premier Leagues NSW organised by Football NSW). The league sits at Level 2 on the Northern New South Wales league system (Level 3 of the overall Australian league system).

The league was formally known as the Northern Second Division (1959-1997) and subsequently the Northern First Division (1998-2013).

The competition consists of 10 teams, who each have a First grade and Reserve grade team. The regular season takes place over 18 rounds, with each team playing each other twice in a home and away format.

From 2024 promotion and relegation was reintroduced. The team in first place at the end of the league season are crowned premiers and promoted to the National Premier League (NPL). The team that finishes 11th in NPL Men’s NNSW will join the teams that finish second, third and fourth in Northern League One in a promotion/relegation play-off series to determine the 12th team in NPL Men’s NNSW.

From 2025 the team that finishes last (10th) is relegated to Zone League One, while the Zone League One champion is promoted to Northern League One with no play-off series.

After Sydney clubs broke away from the NSW Football Association in 1958, the Northern NSW Soccer Federation was created by Newcastle and Coalfields clubs.

An 8-team Northern Division Two was established with: Austral Dutch, Courtaulds, Jesmond, Kahibah, Kurri Kurri, Weston, Whitebridge and Young Wallsend.

The following teams are competing in the 2025 season.