| Competition: | Campeonato de Portugal |
| Season: | 2017–18 |
| Promoted: | Mafra Farense |
| Matches: | 1230 |
| Prevseason: | 2016–17 |
| Nextseason: | 2018–19 |
The 2017–18 Campeonato de Portugal is the fifth season of Portuguese football's renovated third-tier league, since the merging of the Segunda Divisão and Terceira Divisão in 2013, and the third season under the current Campeonato de Portugal title. A total of 80 teams compete in this division, which began on 20 August 2017 and ended on 10 June 2018.
The competition format consists of two stages. In the first stage, the 80 clubs will be divided in five series of 16 teams, according to geographic criteria. In each series, teams play against each other in a home-and-away double round-robin system.
In the second stage, the five best-placed teams from each first-stage series and the best three runners-up will dispute a series of playoff matches to promote to the LigaPro. The two finalists will be promoted directly. The six bottom clubs of each series will be relegated.
Relegated from the 2016–17 LigaPro:
From the 2016–17 Campeonato de Portugal:
Promoted from the 2016–17 District Championships:[1]
The 5 winners and the best 3 runners-up were qualified to the knockout stage, where the winning team and the runner-up were promoted to Segunda Liga.