will provide US music fans with more than 2m songs from 180,000 artists in an entirely DRM-free format, making it the world's largest DRM-free MP3 digital music download store, according to the retailer.
The service has been launched following an extensive private beta test, and will provide US-based customers with a service undercutting ' prices.
Individual tracks will cost between 89 and 99 cents, with albums retailing for between $5.99 and $9.99. iTunes charges between 99 cents and $1.29 for individual tracks.
The Amazon music store is currently offering tracks from artists including Amy Winehouse, Coldplay, Paul McCartney and Radiohead, but does not feature artists signed to Sony BMG yet.
It is unknown when the service might be available to Amazon's European customers.
Amazon has completed file-sharing deals with Universal Music Group and Vivendi in the last month.
Apple's iTunes is the dominant player in the US digital music download market, with a 70% share.
Industry analysts have said Amazon MP3 will give customers more choice by offering tracks that were DRM-free, allowing them to play tracks on a wider range of music players.
Amazon may also benefit from its substantial global customer base, making it easier to market its music service.
Bill Carr, vice-president of digital music at Amazon.com, said: "Amazon MP3 is an all MP3, DRM-free catalogue of a la carte music from major labels and independent labels, playable on any device, in high quality audio, at low prices.
"This new digital music service has already been through an extensive private beta, and we're excited to offer it to our customers as a fully functional public beta."