Available in black or white versions, the Nexus 5 costs $349 for a 16GB unlocked version or $399 for 32GB phone, cheaper than Apple's new iPhone 5s and 5c.
The iPhone 5c, the cheaper of Apple's new offerings, costs $549 for a 16GB version if purchased without a wireless contract.
The Nexus 5, available through most major carriers or online through the Google Play store, has a 5-inch display and is tightly integrated with Google search and Google Now, the company's personal-assistant technology.
"This is a cutting-edge device at an incredible price," Sundar Pichai, who heads Google's Android business, told USA Today.
The device, built for Google by South Korea's LG Electronics, will be delivered with the latest version of the Android operating system, KitKat 4.4