Musashi-Kosugi Station (武蔵小杉駅, Musashi-Kosugi-eki) is a pair of physically separated interchange passenger railway stations, a block from each other, located in Nakahara Ward of eastern Kawasaki, Kanagawa, Japan, operated by East Japan Railway Company (JR East) and the private-sector railway operator Tokyu Corporation. Note that the term JR East Musashi-Kosugi Station is non-specific, the physical buildings of the Yokosuka and Nambu lines run by the same company are some 400 meters away, connected by a passageway.

There are essentially two complexes that make up Musashi-Kosugi Station, with a 400-meter connector passageway between them. The western complex contains a Nambu Line JR East station and a Tokyu station in one building. The eastern station is part of the Tokaido Line and contains JR East Yokosuka Line as well as Shinkansen tracks, though the Shinkansen tracks have no stop. Although it is common to name stations after their operator, the term JR East Musashi-Kosugi Station is therefore non-specific as JR East services both complexes.

Musashi-Kosugi Station is served by JR East's Nambu Line, Yokosuka Line, and Shōnan-Shinjuku Line, as well as Tokyu's Tōyoko Line and Meguro Line.

JR Musashi-Kosugi Station has two opposed side platforms serving the two tracks (Platform 1 and Platform 2) of the Nambu Line and two side platforms serving the two tracks (Platform 3 and Platform 4) of the Yokosuka Line. The Shōnan-Shinjuku Line and Narita Express share the Yokosuka Line platforms. The two sections of the JR station are located separately and connected by a 400 m-long (1,300 ft) passage. All platforms are elevated, as is the station building. The station has a Midori no Madoguchi staffed ticket office.

Since December 2023, the new "Tsunashima Road" ticket gate and entrance, located between the Nambu Line and Yokosuka Line platforms, have been open to the public. This entrance provides a faster transfer between the Yokosuka Line platforms and the Tōkyū Railways station, eliminating the need to traverse the Nambu Line platform and helping to reduce congestion.

Tokyu Musashi-Kosugi Station has two island platforms serving four tracks. The outer tracks (Platform 1 and Platform 4) are used by the Tokyu Toyoko Line, and the inner tracks (Platform 2 and Platform 3) are used by the Tokyu Meguro Line. All platforms are elevated, as is the station building.

The area around the station was served by the Nambu and Toyoko lines since the 1920s, but over an extended period of time it was integrated as Musashi-Kosugi Station in 1945. Since then, the station has functioned as a major transfer point for people residing in Kawasaki (along the Nambu Line) who commute to Tokyo.

Although the station was already a major station along the two lines in the 1990s, the station started further expansion of its role when the Meguro Line opened in 2000 with direct service to the Tokyo subway lines. The 2010 opening of the new platform for the Yokosuka Line and Shōnan-Shinjuku Line connected the station with many directions in Kantō region, including Narita Airport.