An e-book reader, also called an e-book device or e-reader, is a mobile electronic device that is designed primarily for the purpose of reading digital e-books and periodicals.

Any device that can display text on a screen may act as an e-book reader, but specialised e-book reader designs may optimise portability, readability (especially in sunlight), and battery life for this purpose. A single e-book reader is capable of holding the digital equivalent of hundreds of printed texts with no added bulk or measurable mass.