Samsung and T-Mobile USA today announced the Samsung Galaxy S 4G, which will be compatible with T-Mobile’s HSPA+ network. 

T-Mobile is calling the Galaxy S 4G “the fastest smartphone running on America’s largest 4G Network,” as the company has decided to brand its newest network with the 4G moniker.

The Galaxy S 4G will come running Android 2.2 (Froyo) and features Samsung’s Super AMOLED display. T-Mobile says the new phone will see “theoretical peak download speeds of up to 21 Mbps.” T-Mobile promises more detailed information on the Galaxy S 4G in the coming weeks.

T-Mobile’s HSPA+ network is currently available in 100 major metropolitan areas, reaching approximately 200 million people nationwide. At CES, T-Mobile announced that it will bump its HSPA+ network up to theoretical speeds of 42 Mbps. 

Samsung has done well with its Galaxy S line of smartphones. In February, JK Shin, president and head of mobile communications business at Samsung, told Reuters that the company planned to triple its smartphone production by the end of the 2010. “I will totally commit myself to this goal,” Shin told Reuters.

Since then, variants of the company’s Galaxy S smartphones have made it to every major carrier in the United States, and the company made good on its word. On Jan. 6, the company announced that it had sold 10 million Galaxy S smartphones since the line launched in June 2010.