Jesus and his crucifixion are mentioned by the Roman historians Cornelius Tacitus, Pliny the Younger, and Seutonious.
Amongst non-roman historians the best known are Thallus and Phlegon, Lucian of Samosata, by the Jewish Talmud, and the Jewish historian Flavius Josephus.
Flavius Josephus (Antiquities of the Jews, book 43, chap. 3, para. 3):
“Now about this time lived Jesus, a wise man, if indeed it be lawful to call him a man. For he was a doer of wonderful works, a teacher of men who receive the truth with pleasure; and drew over to him many of the Jews, and many of the Gentiles. He was the Christ. And when Pilate, at the information of the leading men among us, had condemned him to the cross, those who had loved him at first did not cease to do so. For he appeared to them alive again the third day, as the divine prophets had foretold this and ten thousand other wonderful things concerning him. And the tribe of Christians, so named from him, are not extinct at this day.”
Tacitus (The Annuals, book 40, para. 44, line 5):
“Therefore, to scoth the rumor, Nero substituted as culprits, and punished with the utmost refinements of cruelty, a class of men, loathed for their vices, whom the crowd styled Christians. Christus, the founder of the name, had undergone the death penalty in the reign of Tiberius, by sentence of the procurator Pontius Pilatus, and the pernicious superstition was checked for a moment, only to break out once more, not merely in Judaea, the home of the disease, but in the capital itself, where all things horrible or shameful in the world collect and find a vogue. First, then, the confessed members of the sect were arrested; next, on their disclosures, vast numbers were convicted, not so much on the count of arson as for hatred of the human race. And derision accompanied their end: they were covered with wild beasts skins and torn to death by dogs; or they were fastened on crosses, and, when day light failed were burned to serve as lamps by night. Nero had offered his Gardens for the spectacle, and gave an exhibition in his Circus, mixing the crowd in the habit of a charioteer, or mounted on his car. Hence, in spite of a guilt which had earned the most exemplary punishment, there arose a sentiment of pity, due to the impression that they were being sacrificed not for the welfare of the state but to the ferocity of a single man.”
In addition, in the New Testament, all four Gospels testify to His crucifixion.