Filyovskaya line (until 1971 — Arbatsko-Filyovskaya) is the fourth line of the Moscow metro. It runs in the western part of the city through the historic district of Fili, which explains its name. One of the two lines of the Moscow metro (the second is the Butovskaya line), most of which is located on the surface. Most of the stations on the line are short, designed to receive trains of a maximum of six standard carriages. Also, there are many curves and slopes on the alignment of the line. On the diagrams, it is indicated in blue and numbers: for the route to Kuntsevskaya and to Mezhdunarodnaya (until December 2020, the entire line was indicated by the number 4).

The official number of the line is four, but according to the opening date it is the sixth (the official opening date of the line is November 7, 1958, while the Riga radius of the Kaluzhsko-Riga line was opened several months earlier), and from 1958 to 1990 designated as «3-A» and was considered one of the contours of the Arbatsko-Pokrovskaya line. At the same time, the first section of the Filyovskaya line («Kominterna Street» — «Smolenskaya») was opened in general as part of the first stage in the form of a forklift movement on the then Kirov diameter (now Sokolnicheskaya) line.

The average daily passenger traffic of the line in 2011 was 143 thousand people.