Made by LG, the handset is smaller, slimmer and lighter than the Nexus 4 but its 4.96in (126mm) touchscreen is bigger.
The Nexus 5 has been developed to show off the capabilities of the new version of the Android operating system.
Called Kitkat, the software has been designed to work well on both high-end smartphones and cheaper feature phones.
The alliance with Google has helped bolster LG’s fortunes even though, according to statistics from Gartner, it is still a long way behind rivals Samsung and Apple.
In the April-to-June quarter, the consultancy indicated 3.8% of all smartphones sold were LG handsets putting the South Korean firm in third place.
By contrast, Apple accounted for 18.8% of all sales and Samsung 29.7%.
The specifications for the new phone were widely leaked before it was announced on the official Google blog.
The gadget shares some of the hardware from LG’s G2 handset and can record and play back HD video at the full 1080p resolution. Its camera also has a rapid burst system that captures several photographs at the same time so owners can pick the best shot.
The handset is due to go on sale on 1 November in the US, UK, Canada, Australia, France, Germany, Spain, Italy, Japan and Korea.
“Nexus devices serve an important function for Google,” said Ben Wood, head of research at analyst firm CCS Insight.
“The company collaborates closely with the chosen phone maker as it rolls out a new version of the Android operating system and this results in a ‘vanilla’ version of the software that acts as a reference platform for developers and tech enthusiasts.”
Google said a base 16GB version of the device would cost $349 in the US (£299 in the UK), unlocked and without a contract. The 32GB version should cost $399 (£339 in the UK).
With Android Kitkat, Google said it had made the software use less memory so it could be used on handsets with much lower specifications than top end smartphones.
In addition, Google has begun moving some services off Android’s core software and onto its app store. Many see this as a way for it to maintain more control over the security of the software and its associated applications.