Are Christians considered disbelievers or polytheists?

All perfect praise be to Allaah, The Lord of the Worlds.  I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Disbelief and polytheism are two faces of the same coin. In other words, the disbeliever is necessarily a polytheist and vice versa. This is because disbelief and Shirk are inseparable. The People of the Book, whether Jews or Christians, are clearly described as both disbelievers and polytheists in the Quran. They are described as disbelievers in the following verses (which mean):

•        {They have certainly disbelieved who say, "Allaah is the Messiah, the son of Mary" while the Messiah has said, "O Children of Israel, worship Allaah, my Lord and your Lord." Indeed, he who associates others with Allaah -“Allaah has forbidden him Paradise, and his refuge is the Fire. And there are not for the wrongdoers any helpers.}[Quran 5:72]

•        {Those who disbelieved among the People of the Scripture and the polytheists were not to be parted [from disbelief] until there came to them clear evidence.}[Quran 98:1]

There are many other verses that describe them as disbelievers. They are described as polytheists in the words of Allaah The Exalted (which mean): {They have taken their scholars and monks as lords besides Allaah, and [also] the Messiah, the son of Mary. And they were not commanded except to worship one God; there is no deity except Him. Exalted is He above whatever they associate with Him.}[Quran 9:31] There are other verses where they claimed that Allaah The Almighty had taken a wife and a son. It goes without saying that this is one kind of Shirk.

Allaah Knows best.