The Boulevard Line (Danish: Boulevardbanen) is a 3.2-kilometer (2.0 mi) long partly underground railway between Copenhagen Central Station and Østerport Station in Copenhagen, Denmark.

Out of the four main S-train branches, three follow this path, between Dybbølsbro and Svanemøllen (with at least four tracks).

Only at Copenhagen Central, Nørreport and Østerport do all trains stop.

While Dybbølsbro, Vesterport, Nordhavn and Svanemøllen all are S-train stations only.

(Nørreport also has Metro service, just as both the Central Station, Østerport and Nordhavn have since 2019).