Many religions were there before the holy prophet.
There were a vast number of pagan and henotheistic cults along with heretical Christian and Jewish sects. Arabia was a number of autonomous city-states and each tribe had a different religion to which they adhered.
The main religion of Saudi Arabia is Islam
Islam started in Arabia 1432 years ago _______________________________________________________ It was the immigration of prophet Muhammad (PBUH) from 1432 years ago and not the religion start. The religion that had begun in the currently called Saudi Arabia is the full submission to God and surrender to His will (called in Arabic Islam). This is the religion since start of mankind in the area from the prophet Adam, Noah, ..., Abraham, ..., Moses,..., Jesus, and Muhammad (peace be upon them).
Islam is an Abrahamic religion, and thus has its roots in Judaism and is connected to Christianity, as they all worship the same god. Islam originated with the prophet Muhammad, who Muslims believe to be a prophet of the god of Abraham.
Saudi Arabia's primary religion (along with most of the Middle East) is Islam.
The birth city of prophet Muhammad (PBUH) is Makkah (or Mecca) in Saudi Arabia. The city that the prophet immigrated to and buried in is Medina (in Saudi Arabia too).
Saudi Arabia
Saudi Arabia & Egypt
Saudi Arabia is known as the 'birth place' of a more specific religion, Islam.
The vast majority of Saudi are Wahhabi Muslims. Being any religion other Muslim is illegal in Saudi Arabia.
Islam, since being a citizen of Saudi Arabia legally requires you to be a Muslim.
He is an Arabic Man and born in the currently called Kingdom of Saudi Arabia.
No God prophet was born in Medina in Saudi Arabia.