When I hear people ask who the Two Witnesses are, responses often jump to Moses and Elijah, Enoch and Elijah, Zechariah, Haggai, and others guesses. It seems to me the Bible tells us who the Two Witnesses are by defining that they are the Two Olive Trees and the Two Lampstands.
The Two Lampstands are the more straightforward of the two.
As for the mystery of the seven stars that you saw in my right hand, and the seven golden lampstands, the seven stars are the angels of the seven churches, and the seven lampstands are the seven churches.
Out of the seven churches addressed in Revelations, only two are not rebuked- Smyrna and Philadelphia. Both are given direction to endure, conquer, and remain steadfast during the tribulation and the hour of testing. Would it logically follow that the Two Lampstands seem to represent the non-rebuked Church that must endure and conquer in the coming Tribulation? This fits with what the Bible says the Two Olive Trees are.
16 The Lord once called you ‘a green olive tree, beautiful with good fruit.’ But with the roar of a great tempest he will set fire to it, and its branches will be consumed. 17 The Lord of hosts, who planted you, has decreed disaster against you, because of the evil that the house of Israel and the house of Judah have done, provoking me to anger by making offerings to Baal.”
This is the starting point for the Two Olive Trees representing the House of Israel and the House of Judah. Then in Ezekiel, the Hebrew word for "stick" is "ets" meaning tree. The two sticks/trees represent the House of Israel and the House of Judah that will be united as one.
16 “Son of man, take a stick and write on it, ‘For Judah, and the people of Israel associated with him’; then take another stick and write on it, ‘For Joseph (the stick of Ephraim) and all the house of Israel associated with him.’ 17 And join them one to another into one stick, that they may become one in your hand. 18 And when your people say to you, ‘Will you not tell us what you mean by these?’ 19 say to them, Thus says the Lord God: Behold, I am about to take the stick of Joseph (that is in the hand of Ephraim) and the tribes of Israel associated with him. And I will join with it the stick of Judah, and make them one stick, that they may be one in my hand. 20 When the sticks on which you write are in your hand before their eyes, 21 then say to them, Thus says the Lord God: Behold, I will take the people of Israel from the nations among which they have gone, and will gather them from all around, and bring them to their own land. 22 And I will make them one nation in the land, on the mountains of Israel. And one king shall be king over them all, and they shall be no longer two nations, and no longer divided into two kingdoms.
So we have this picture of the Two Olive Trees being the House of Israel and the House of Judah, and the Two Lampstands as the remnant Church. How do these fit together into the Two Witnesses?
Romans 11:17-24 says we are the Wild Olive Tree grated into the cultivated tree (Israel and Judah joined).
17 But if some of the branches were broken off, and you, although a wild olive shoot, were grafted in among the others and now share in the nourishing root of the olive tree, 18 do not be arrogant toward the branches. If you are, remember it is not you who support the root, but the root that supports you. 19 Then you will say, “Branches were broken off so that I might be grafted in.” 20 That is true. They were broken off because of their unbelief, but you stand fast through faith. So do not become proud, but fear. 21 For if God did not spare the natural branches, neither will he spare you. 22 Note then the kindness and the severity of God: severity toward those who have fallen, but God’s kindness to you, provided you continue in his kindness. Otherwise you too will be cut off. 23 And even they, if they do not continue in their unbelief, will be grafted in, for God has the power to graft them in again. 24 For if you were cut from what is by nature a wild olive tree, and grafted, contrary to nature, into a cultivated olive tree, how much more will these, the natural branches, be grafted back into their own olive tree.
The last verse of Revelation 10 says:
11 And I was told, “You must again prophesy about many peoples and nations and languages and kings.” Which then leads right into the talk of the Two Witnesses. I don't see two lone individuals described there, but a multitude.
Many more points to make but just a couple more from Chapter 11.
And when they have finished their testimony, the beast that rises from the bottomless pit will make war on them and conquer them and kill them, (the Two Witnesses)
The idea of the Two Witnesses representing a larger number than two individuals is supported in chapters 12 & 13 when the beast makes war on "them" and is defined further:
Revelation 13:7, 10
7 Also it was allowed to make war on the saints and to conquer them. And authority was given it over every tribe and people and language and nation, ... 10 If anyone is to be taken captive, to captivity he goes; if anyone is to be slain with the sword, with the sword must he be slain. Here is a call for the endurance and faith of the saints.
Then the dragon became furious with the woman and went off to make war on the rest of her offspring, on those who keep the commandments of God and hold to the testimony of Jesus. And he stood on the sand of the sea.
After they have been killed, Revelation 11:11-12 says:
11 But after the three and a half days a breath of life from God entered them, and they stood up on their feet, and great fear fell on those who saw them. 12 Then they heard a loud voice from heaven saying to them, “Come up here!” And they went up to heaven in a cloud, and their enemies watched them.
Note the similarity here in 1 Thessalonians 4:16b-17 (as well as many other verses) describing the first resurrection:
16 ... And the dead in Christ will rise first. 17 Then we who are alive, who are left, will be caught up together with them in the clouds to meet the Lord in the air, and so we will always be with the Lord.
Are we not His Witnesses?