Flavius Josephus’ Antiquities of the Jews

Flavius Josephus,a Palestinian, wrote his Antiquities of the Jews to educate the Roman-Hellenistic world about Judaism and the Jews. In it, he recounts the tale of the Watchers as follows:

For many angels of God accompanied with women, and begat sons that proved unjust, and despisers of all that was good, on account of the confidence they had in their own strength; for the tradition is, that these men did what resembled the acts of those whom the Grecians call giants. But Noah was very uneasy at what they did; and being displeased at their conduct, persuaded them to change their dispositions and their acts for the better: but seeing they did not yield to him, but were slaves to their wicked pleasures, he was afraid they would kill him, together with his wife and children, and those they had married; so he departed out of that land. – 1.72-75

According to Josephus, the union between the fallen angels and human women produced a race of giants, which in antiquity were called Nephilim.