The 2018 1. divisjon (referred to as OBOS-ligaen for sponsorship reasons) was a Norwegian second-tier football league season.

The season began on 2 April 2018 and ended on 11 November 2018 (not including playoff matches).

Sogndal, Aalesund and Viking were relegated from the 2017 Eliteserien, while HamKam, Nest-Sotra and Notodden were promoted from the 2017 2. divisjon.

The 3rd to 6th placed teams took part in the promotion play-offs; these were single leg knockout matches.

KFUM Oslo won 4-3 on aggregate and were therefore promoted, while Åsane got relegated.