Line 1 of the Saint Petersburg Metro, also known as Kirovsko-Vyborgskaya Line (Russian: Ки́ровско-Вы́боргская ли́ния) or Red Line, is the oldest rapid transit line in Saint Petersburg, Russia, opened in 1955, which connects Kirovsky and Vyborgsky districts of the city. The original stations are very beautiful and elaborately decorated, especially Avtovo and Narvskaya. The line connects four out of five Saint Petersburg's main railway stations. In 1995, a flooding occurred in a tunnel between Lesnaya and Ploschad Muzhestva stations and, for nine years, the line was separated into two independent segments (the gap was connected by a shuttle bus route). The line is also one of the two lines in the network to feature shallow stations, the other being the Nevsko-Vasileostrovskaya Line.

The line cuts Saint Petersburg centre on a northeast-southwest axis. In the south its alignment follows the shore of the Gulf of Finland. In the north it extends outside the city limits into the Leningrad oblast (it is the only line to stretch beyond the city boundary). The Kirovsko-Vyborgskaya Line is generally coloured red on Metro maps, and markup of this colour has been added to its stations for ease of passenger orientation; the new generation trains of Yubileyniy carriages since 2010s also have their outside colour matching the colour of the line.