Keihin-Tōhoku Line is the name used for a train service running between Ōmiya and Yokohama. Most trains continue on Negishi line so the service is often called Keihin-Tōhoku Line Negishi Line.

As Keihin-Tōhoku Line runs parallel with other lines all the way, it's not considered as an official railway line. At this site the term "virtual line" is used for such lines.
Keihin-Tōhoku Line has its own double track running parallel with Tōhoku Hon Line Ōmiya - Tōkyō and Tōkaido Hon Line Tōkyō - Yokohama. Between Akabane and Tabata, the Keihin-Tōhoku Line is the only service along the original Tōhoku Hon Line route.
Between Higashi-Kanagawa and Yokohama are the Keihin-Tōhoku tracks also used by Yokohama line trains.

The Rapid trains run daytime (~10.00 - 15.00) and skip many stations in central Tōkyō where the line runs parallel to Yamanote line. The Local trains stop at all stations and run at all other times.