We are not told who they are, and so all answers are speculative.

1. Enoch and Elijah (Dake)
2. Symbols of the believing church (Ryken, Mounce)
3. Just two witnesses, but not necessarily anyone from history or anyone special (Beckwith)
4. Symbols of the law and the prophets—witnesses against a sinful world
5. Moses and Elijah (Tenney, Lindsey, Kittel)

Arguments are futile because the issue is unresolvable, and it doesn't matter anyway. There is no possible way to determine who they are. The point is that God, in his justice and desire for repentance and salvation, will continue to issue warnings and reveal himself through prophets, even to the bitter end. In the power of God they will warn of divine judgment and plead for repentance. The point is not to identify them but to show us that God continues to draw all men to Himself and to warn of the dire consequences of defiance. The identity of the prophets is obscure so we get the message instead of dwell on the messengers.

In Revelation 11 we are told there will be two witnesses who will prophecy for 1,260 days clothed in sackcloth. They are described as "the two olive trees and the Two lampstands that stand before the lord of the earth." Who are they, and are they witnessing during the first 3 and a half years of the tribulation or the second half?