Are the Popes the Antichrist?

Yes, if you mean Paul’s man of sin described in II Thess 2:1-10. If you want to understand Bible prophecy like Christians did until the middle of the 19th century, then study Daniel 7:1-28, where the little horn of Rome presented by Daniel is the popes of Rome. After adding Paul’s description already identified, the beast of Revelation 13 is clearly the pope, and the great whore of Revelation 17 is his church. All evangelical churches confessed this in their creeds until very recently. The Westminster Confession of 1647 of the Presbyterians stated it clearly in Chapter XXV about the church until it was revised in 1903. The Baptist London Confession of 1689 still states it in Chapter XXVI.

See Also

Evidence that Catholicism is not Christian: Is Catholicism Christian?
Evidence that Catholicism is Anti-Christ: Is Catholicism Antichrist?
More evidence that the pope is the antichrist: The Antichrist.
The blood of true saints: The Martyrs.