While we already knew it was coming, today T-Mobile officially released details on the Galaxy S 4G.

The Galaxy S 4G is very similar to T-Mobile’s Vibrant, which is also a Galaxy S smartphone. The biggest difference is its support for T-Mobile’s 4G HSPA+ network, where it will deliver theoretical peak download speeds of up to 21Mbps.

The Galaxy S 4G is powered by a 1GHz Samsung Cortex A8 processor and runs Android 2.2 Froyo. It has a 4-inch Super AMOLED display, a pre-installed 16GB microSD card, a 5MP camera capable of recording 720p HD video, and a 1,650mAh battery.

The Galaxy S 4G will also offer “mobile HD TV” and will come with the movie Inception pre-loaded on it.

T-Mobile expects to launch the Galaxy S 4G this month but it did not provide an exact release date or pricing details for the phone.