One who practices the 5 Pillars of Islam and believes in the 6 Fundamental of Faith. One can become a Muslim by saying :

"Ashadhu An Laa ilaaha Allah Wa Ashadhu Anna Mohammed Ar Rasulullah"

This means "I bear witness that no deity has the right to be worshipped except Allah and I bear witness that Mohammed is HIS servant and Final Messenger"

All Prophets preceeding Mohammed were Muslims. This includes Noah, Abraham, Issac, Jacob, Moses and Jesus. Is there doubt that these Prophets did not submit their will to the Creator? 

Allah said in Quran"Abraham was neither a Jew or a Christian but he was a true Muslim and he was not of idolaters"

It is important to note that other religion are derived from the name of a place or person. Example Christianity  is from Jesus Christ.

Islam is the Only Revealed Religion and way of life (DEEN) that directly attaches its worshippers to the servitude of the Creators.