It’s widely known that Facebook is the most popular third-party app on most, if not all, mobile platforms. When it comes to Google’s Android platform though, the first mobile media rankings from Nielsen (July 2011) paint a more interesting picture.

The research firm determined each apps active reach – the percentage of Android owners who used an app within the past 30 days – by analyzing the data from on-device meters on thousands of Android smartphones. Aside from the Android Market app itself, the five most used apps among US Android users 18 years and older were as follows (in order): Google Maps, Gmail, Facebook, Google Search, and YouTube.

This list means that Facebook was overall the third most-used app on Android, and the first most-used third-party app on Android (the other four are all made by Google). It had a 73.5 percent reach, compared to 90.5 percent for the Android Market. The rankings change quite a bit, however, when we break them down to male and female.

For males, the top five apps were Google Maps, Gmail, Google Search, Facebook, and YouTube. With a 66.9 percent reach, Facebook was the fourth most-used Android app by males, and the most-used third-party Android app by males.

For females, the top five apps were Facebook, Gmail, Google Maps, Google Search, and YouTube. With an 81.0 percent reach, Facebook was not only the most-used third-party app by females, but also the most-used Android app by females overall.