The Nephilim are mentioned in Genesis 6.  They are often identified with the Anakim of Numbers 13:33 and the Rephaim of Deut. 2:20.  Let’s take a look.

• “Now it came about, when men began to multiply on the face of the land, and daughters were born to them, ² that the sons of God saw that the daughters of men were beautiful; and they took wives for themselves, whomever they chose. ³ Then the Lord said, “My Spirit shall not strive with man forever, because he also is flesh; nevertheless his days shall be one hundred and twenty years.” ⁴ The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of men, and they bore children to them. Those were the mighty men who were of old, men of renown,” (Gen. 6:1-4).
• “There also we saw the Nephilim (the sons of Anak are part of the Nephilim); and we became like grasshoppers in our own sight, and so we were in their sight,” (Numbers 13:33).

The word “Nephilim” is the untranslated pronunciation of the Hebrew נְפִילִים.  It means giants and was translated in the Septuagint into the Greek γίγαντες, gigantes.  The word is found in only two places, Genesis 6:4 (pre-flood) and Numbers 13:33 (post-flood).

Who are the Nephilim?

There is debate over the identity of the Nephilim in Genesis 6. Some people believe that the Nephilim are the offspring of sexual relations between fallen angels and human women. In support of this view Jude 6 is often referenced:  “And angels who did not keep their own domain, but abandoned their proper abode, He has kept in eternal bonds under darkness for the judgment of the great day,” (Jude 1:6). This would mean that the fallen angels (The Hebrew naphal means ‘to fall’) had sexual intercourse with women. Whether or not this is possible is not explicitly stated in Scripture. However, we do know that angels can appear as humans (Hebrews 13:2) and are exceedingly powerful (2 Peter 2:11), so it is conceivable that they can manifest with total biological capabilities as well.

Another view held by Christians is that the Nephilim are the descendants of Seth, the son of Adam.¹Jamieson, R., A. R. Fausset, and D. Brown, A Commentary, Critical and Explanatory, on the Old and New Testaments, Oak Harbor, WA: Logos Research Systems, 1997, Gen. 6:2-3.  The term “sons of God” would designate great power and authority the same way a king would be addressed with the term “your Majesty.” In this view, the men who were supposed to be godly took wives who were unbelievers and their offspring are said to have been fallen ones.

Finally, there are others, non-Christians, who believe that the Nephilim are aliens from other worlds. This last view is certainly unbiblical.

According to Harper’s Bible Dictionary, the Nephilim are “people of the pre-Flood generation, the offspring of daughters of men and divine beings (Gen. 6:1-4). Their generation and their conduct seem to have provoked the Flood as punishment (Gen. 6:5-8:22).  In Num. 13:33 the Israelite spies describe the inhabitants of Hebron as Nephilim–so large and powerful that ‘we seemed like grasshoppers.’ The name could mean ‘fallen ones’ and allude to stories in related cultures of rebellious giants defeated by the gods in olden times” (cf. Isaiah 14:12).²Achtemeier, Paul J., Harper’s Bible Dictionary, San Francisco: Harper and Row, 1985, 696. Of course, a problem with this view is how did the Nephilim survive the flood? We see a post-flood account of them in Num. 13:33, “There also we saw the Nephilim (the sons of Anak are part of the Nephilim); and we became like grasshoppers in our own sight, and so we were in their sight.”

One issue is the use of the term Nephilim before and after the flood. If all of the inhabitants of the world were destroyed, except for those on Noah’s Ark, then where did the Nephilim of Numbers 13:33 come from? There are two possibilities. First, it could be that if the fallen angels had sex with women before the flood, there’s no reason to conclude that could not have done so again after the flood and produced more giants. Or, it could be that the Nephilim of Numbers 13:33 are large people and were referenced using the pre-flood term.

The range of options is varied. Consider this compilation of quotes:

• “Many have suggested that the sons of God were the godly line of Seth and the daughters of men were the Cainites. But this does not do justice to the terminology or the context. Others view the ‘sons of God’ as angels (as in Job 1:6), who cohabited with women on earth. This, however, conflicts with Matt. 22:30.”³Walvoord, John F., and Roy B. Zuck, The Bible Knowledge Commentary, Wheaton, IL: Scripture Press Publications, 1985.
• “The term [Nephilim, Giants] in Hebrew implies not so much the idea of great stature as of reckless ferocity, impious and daring characters, who spread devastation and carnage far and wide.”⁴Jamieson, Fausset, and Brown, Ge 6:4.
• “The improper mating of heavenly beings and earthly women is an attack on the boundaries that are meant to separate the heavenly and earthly realms. It thus threatens the integrity of creation as God intended it.”⁵Mays, James Luther, ed., Harper’s Bible Commentary, New York: Harper and Row, 1988, Ge 6:5.

As you can see, commentaries are divided on who exactly the Nephilim really are, and the scripture is not clear. Therefore, we can make no definite statement on their identity.