The Ring Line is the newest rapid transit loop line of the Oslo Metro of Oslo, Norway. It connects to the Sognsvann Line in the west and the Grorud Line in the east; along with these two lines and the Common Tunnel, the Ring Line creates a loop serving both the city centre and Nordre Aker borough. The 5.0 kilometres (3.1 mi)-long line has three stations: Nydalen, Storo and Sinsen. Four-fifths of the line runs within two tunnels, with the 1.0-kilometer (0.62 mi) section between Storo and Sinsen, including both stations, being the only at-grade part. The line connects to the Grorud Line north of Carl Berners plass and with the Sognsvann Line north of Ullevål stadion.

The Oslo Metro is the rapid transit system of Oslo, Norway, operated by Sporveien T-banen on contract from the transit authority Ruter. The network consists of five lines that all run through the city centre, with a total length of 85 kilometres (53 mi), serving 101 stations of which 17 are underground or indoors. In addition to serving 14 out of the 15 boroughs of Oslo, two lines run to Kolsås and Østerås, in the neighbouring municipality of Bærum. In 2016, the system had an annual ridership of 118 million.