That's up 100 million users from March, when the company said that the service had 600 million monthly users.
Facebook has been ramping up its efforts into building Messenger as a standalone social platform, with its own features and capabilities that are separate from the flagship Facebook social network. In March Facebook allowed third-party software deveopers to create apps to run inside of Messenger.
Messenger is one of several such standalone services in Facebook's arsenal. It also owns the Whatsapp messaging service, which counts 800 million monthly users and the Instagram photo app which has more than 300 million users.
Facebook Messenger boss David Marcus also noted that the Messenger app has been downloaded more than 1 billion times on Android devices.