Those who don't believe in God are guilty of rejecting God, for whether or not they have heard about Him, they know about Him instinctively, per the Word of God. There will be "no excuse" when they stand before the throne:
Matthew 12:30 "He who is not with Me is against Me."
John 15:22 "If I had not come and spoken to them, they would not have sin, but now they have no excuse for their sin."
Romans 1:20 "For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse."
Revelation 12:20 & 30 "And I saw the dead, the great and the small, standing before the throne, and books were opened; and another book was opened, which is the book of life; and the dead were judged from the things which were written in the books, according to their deeds...And if anyone's name was not found written in the book of life, he was thrown into the lake of fire."