The Superliner is a largely disabled-accessible double decker passenger car used by Amtrak, on mainly its western routes. They come in coach, baggage coach, diner, lounge, coach cafe, sleeper, and transition car/dorm configurations. Trains using Superliners include the Capitol Limited, Auto Train, Sunset Limited, Texas Eagle, California Zephyr, Southwest Chief, Empire Builder, Coast Starlight, and Pacific Surfliner.

The overall design of the Superliner cars was based on (and fully compatible with) cars designed and owned by the Santa Fe railroad, for their El Capitan all-coach train. For some years, while much of the Superliner fleet was still under construction, refurbished El Capitan coaches were included in many Superliner consists; in recent years, four El Capitan lounge cars were pulled out of storage and refurbished as the Coast Starlight's "Pacific Parlor" first-class lounge cars. These refurbished cars have a service bar, booths, and chairs on the upper level, and were recently upgraded to have a theatre on the lower level.

Superliner sleeping cars have five deluxe bedrooms, ten economy bedrooms (the latter variously known as "Superliner Standard Bedrooms" and "Superliner Roomettes") and a single shared toilet for the economy room passengers on the upper level, and four more economy rooms, a "family" room, three more shared toilets, a shared shower, luggage racks, the vestibule, and an "accessible" room on the lower level. Since passage from car to car at the lower level is neither necessary nor possible on Superliner cars, the "family" and "accessible" rooms run the entire width of the car.

Superliner dining cars have almost the entire upper level available for seating, while the kitchen fills the entire lower level.

Superliner lounge cars once had an operating wet-bar on the upper level; this function has been consolidated with that of the snack bar on the lower level, but the abandoned upper-level bars have not yet been removed.

Superliner coaches typically have four unisex toilets (one with a changing room), an accessible toilet, and a dedicated women's restroom on the lower level as well as baggage racks, and either an accessible coach section, a children's playroom, or, on those few trains that permit smoking on board, a smoking lounge.

The original El Capitan cars were built by the Budd Company, while the Superliners were built by Pullman-Standard and Bombardier.