The app, which can be downloaded for free from the App Store and the Android Market now, allows Facebook members with an Apple iPhone or Google Android device to send messages to others member of the social network. Facebook says the messages will be delivered through notifications and texts, "so your friends are more likely to get them right away".
The messages can be sent to online and offline contacts and there's even a group messaging function.
Furthermore, users can able to access their whole history of conversations whether via email, messages and chats (Facebook's equivalent of instant messages) from their handset as well as when they log on to the social network.
"We think messaging should be easier than that. You should be able to write a message, click 'Send' and know that you will reach the person right away. So, we're introducing Messenger, a new mobile app that simplifies how messaging works, and gives you a faster way to message friends and small groups," Facebook said when it launched the service in the US last month.