The Zamoskvoretskaya line, formerly Gorkovsko–Zamoskvoretskaya (Го́рьковско-Замоскворе́цкая), is a line of the Moscow Metro. Opened in 1938, chronologically it became the third line. There are 24 stations on the Zamoskvoretskaya line, and it spans 42.8 kilometres (26.6 mi), roughly crossing Moscow in a north–south direction. A normal trip along the entire line takes 55 minutes, with the trains on the line averaging 42 kilometres per hour (26 mph). While most of the line is underground, there are some pockets of surface-level or above-ground track, mainly at the point where the line crosses the Moskva River. The line contains many examples of original Moscow Metro architecture, and contains arguably the most photographed station on the entire network: Mayakovskaya.

The Moscow Metro is a metro system serving the Russian capital of Moscow as well as the neighbouring cities of Krasnogorsk, Reutov, Lyubertsy and Kotelniki in Moscow Oblast. Opened in 1935 with one 11-kilometre (6.8 mi) line and 13 stations, it was the first underground railway system in the Soviet Union.