The 2021 Norwegian Second Division (referred to as PostNord-ligaen for sponsorship reasons) was a Norwegian football third-tier league season. The league consisted of 28 teams divided into 2 groups of 14 teams. The league was played as a double round-robin tournament, where all teams played 26 matches. The season started on 19 June 2021 and concluded on 14 November 2021. Kongsvinger earned promotion from group 1 on 23 October 2021, three rounds before the end of the season. Skeid secured promotion from group 2 on 6 November 2021, following a 12–0 win against Rosenborg 2.