There seems to be a lot of debate over who is the messiah in both the anime and the manga. The answers are Sailormoon and Mistress 9 and Sailormoon and Sailorsaturn respectively.

Many think that Saturn is the Messiah in the anime but she isn't. Mistress 9 clearly declares that SHE is the Messiah of Silence in her appearance in Episode 123

Sailormoon is the other messiah. It is true that Uranus and Neptune tell her she isn't in Episode 111 because she fainted after using only a little of the Grail's power. But in the end she is able to transform without the Sacred Cup and goes to get Hotaru. A while after the battle is won (episode 126), Sailoruranus and Sailorneptune go to see her and demand a fight. When she wins they bow and tell her she is truly worthy of her position as future queen. They also add that they have completed their mission of finding the true Messiah.

"You're as good as I expected Princess... I mean, future Queen" said Sailor Neptune.
"Thank you for showing us your great power at the last moment," said Sailor Uranus.
"We've completed our mission before departing," said Sailor Neptune.
"We found the true messiah at last," said Uranus, "and saved the Earth."
"The true messiah?" asked Sailor Moon, "Who is it?"
Neptune and Uranus laughed. "Always the same," commented Sailor Uranus.

In the manga it is both Super Sailormoon (or something like that) and Saturn. Saturn brings down her glaive and marvels at the beauty of destruction. Moon tells her they will both be destroyed but Saturn is aware of this. She says with death there is rebirth and that Super Sailormoon would be the cause. Saturn tells Pluto to close the time-space door and Saturn fades away. Moon thinks about what she said and appears in her princess gown and everything starts to repair itself. Mamoru thinks somthing like "So you are the messiah." Hotaru is reborn and everything is OK.

If that doesn't do it for you, here are Naoko Takeuchi's exact words about two of the pictures in her third artbook which are featured in the image above.

This Saturn is drawn on top of tracing paper. Under that, I pasted tone with copied decoration, I pasted color copy and seals, and then I put it on cardboard. I love cutting and pasting! Oh, it's fun. I use ball-point pen for the gold parts. This is one of the messiahs, Sailor Saturn.

And now the other messiah. The column where Selenity is standing I drew while looking at a picture of a column of an ancient temple of the Roman Forum I took when I went in the fall of '94. The whole city of Rome is filled with historic ruins, a city so full of history it's dizzying. With these two opposite pages, I've put together the two messiahs.

These tranlations are by Alex Glover (of course) and are availible at Manga Style

So there you have it. If you disagree, feel free to e-mail me with solid evidence and I will change this section. Otherwise, I am pretty sure I am right based on the translations I have. ^^

Too Black to be Dawn