Foster is a station on the Chicago Transit Authority's 'L' system, on the Purple Line in Evanston, Illinois.

Like the rest of the 'L' tracks north of the Wilson station, Foster is elevated on a solid fill embankment, unlike the steel structure commonly associated with the 'L'.

It lacks a formal station house; two staircases on the south side of Foster Street lead up to a small area containing a customer assistant's booth, a farecard vending machine, and two turnstiles.

The island platform is composed of concrete and stretches north from the station entrance, covered by a canopy its entire length.

Like Noyes and Central, Foster had an additional side platform to the west of the southbound track for exclusive use of the North Shore Line, to prevent disembarking customers from transferring to 'L' trains for free.