According to Wikipedia:
The Antichrist is a Christian concept based on interpretation of passages in the New Testament, in which the term “Antichrist” occurs five times in 1 John and 2 John, once in plural form and four times in the singular.
1 John 2:
18 – Dear children, this is the last hour; and as you have heard that the Antichrist is coming, even now many Antichrists have come. This is how we know it is the last hour.
22 – Who is the liar? It is the man who denies that Jesus is the Christ. Such a man is the Antichrist–he denies the Father and the Son.
23 – No one who denies the Son has the Father; whoever acknowledges the Son has the Father also.
1 John 4:
3 – but every spirit that does not acknowledge Jesus is not from God. This is the spirit of the Antichrist, which you have heard is coming and even now is already in the world.
2 John 1:
7 – Many deceivers, who do not acknowledge Jesus Christ as coming in the flesh, have gone out into the world. Any such person is the deceiver and the Antichrist.