Flavius Josephus is perhaps the most highly respected and most extensively quoted Jewish historian of all time, he lived from 37-100 C.E. One paragraph in particular from his work by the name "The Antiquities of the Jews" is a favourite of many Christian apologists. It reads as follows:
At first glance it would appear that Josephus is confirming nearly every aspect of the gospel story in one paragraph, but there are several problems with this. Josephus was an orthodox Jew, he did not believe that Jesus was the Jewish Messiah, and besides this one paragraph, Christianity is not mentioned once in all the rest of the collected works of Josephus."Now, there was about this time, Jesus, a wise man, if it be lawful to call him a man, for he was a doer of wonderful works, a teacher of such men as receive the truth with pleasure. He drew over to him both many of the Jews, and many of the Gentiles. He was the Christ; and when Pilate, at the suggestion of the principal men amongst us, had condemned him to the cross, those that loved him at the first did not forsake him, for he appeared to them alive again the third day, as the divine prophets had foretold these and ten thousand other wonderful things concerning him; and the tribe of Christians, so named from him, are not extinct at this day."– Josephus (aka Joseph ben Matthias) The Antiquities of the Jews, Book 18, Chapter 3: the so-called Testimonium Flavianum.
Scholars came to the conclusion a long time ago that the Testimonium Flavianum was fraudulently added into the text at a much later date by Christians. It is worthy to note that the works of nearly every single other Jewish historian that was a contemporary of Josephus had their work burned at the hands of the early church.
The paragraph is exceptionally out of place in Antiquities 18, which is all about misfortunate events that happened to the Jews during that time. In the chapter where the testimonium was inserted, Josephus mentions about a Jewish protest against Pilate where the Romans attacked the Jews with concealed weapons. Out of nowhere appears a paragraph about the Messiah, then immediately afterwards, Josephus writes "And about the same time another terrible misfortune confounded the Jews". In fact the chapter reads much better with the Testimonium removed completely, then the line I just quoted makes sense.
On top of the contextual criticism, is the fact that not a single person quoted the Testimonium until the 4th century, over 200 years after Josephus' death. Not even Justin, Irenaeus, Clement of Alexandria or Tertullian make a reference to this paragraph. Origen, one of the early church fathers from the third century, quoted extensively from the works of Josephus, but didn't quote this paragraph. Origen even wrote that Josephus didn't believe in Jesus.
There are a few other criticisms of the passage in Antiquities 18 that I will not go into, but I think this is sufficient enough to show that Josephus cannot be used as evidence that the Christian account is true, as the Testimonium Flavianum is obviously a fake.