Revelation 18:1-3 NASB
After these things I saw another angel coming down from heaven, having great authority, and the earth was illumined with his glory.  And he cried out with a mighty voice, saying, “allen, fallen is Babylon the great! She has become a dwelling place of demons and a prison of every unclean spirit, and a prison of every unclean and hateful bird.  For all the nations have drunk of the wine of the passion of her immorality, and the kings of the earth have committed acts of immorality with her, and the merchants of the earth have become rich by the wealth of her sensuality.”
Who or what is Babylon? In the last sentence of chapter 17 it tell us that the woman that John saw is the great city that rules over the kings of the earth. In John’s time that city was Rome. Rome was an enemy of God and persecuted many Christians. Babylon represents any evil city, nation, place or even government systems. It has great influence over people with material possessions, luxuries, wealth and the worship of anything other than God.