Sheik

A mysterious warrior with great wisdom and strength. Sheik is a Sheikah, as revealed when he first confronts Link in the Temple of Time. He describes himself as the last remaining survivor of the Sheikah tribe. Sheik helps Link along his quest while he never reveals who he is and why he is aiding Link. His advice and knowledge of the world make him a great ally in the Link's quest.

It is later revealed in the game, that Sheik is actually Princess Zelda. This would suggest that Princess Ruto's remarks about Sheik's gender are erroneous and that she was not aware of her true identity.

Various fan theories exist concerning Sheik's true gender, but the one most supported by evidence from OoT itself is that Sheik is Princess Zelda in a masculine disguise. In Super Smash Bros. Melee, Sheik's profile describes the warrior as being "she". But, if you read the Japanese strategy guide, it explains that she used magic to literally turn herself into a boy...

However, considering that Sheik was nothing more than a character, designed by Zelda to hide her true Identity, Sheik's identity would be whatever Zelda was trying to appear as. As the clothing is mainly male, Sheik can be said to be male.

Quotes
Sheik, in Link's first meeting with him in the Temple of Time:

I've been waiting for you, Hero of Time... When evil rules all, an awakening voice from the Sacred Realm will call those destined to be Sages, who dwell in the five temples. One in a deep forest... One on a high mountain... One under a vast lake... One within the house of the dead... One inside a goddess of the sand... Together with the Hero of Time, the awakened ones will bind the evil and return the light of peace to the world... This is the legend of the temples passed down by my people, the Sheikah. I am Sheik. Survivor of the Sheikahs... As I see you standing there holding the mythical Master Sword, you really do look like the legendary Hero of Time... If you believe the legend, you have no choice. You must look for the five temples and awaken the five Sages... One Sage is waiting for the time of awakening in the Forest Temple. The Sage is a girl I am sure you know... Because of the evil power in the temple, she cannot hear the awakening call from the Sacred Realm... Unfortunately, equipped as you currently are, you cannot even enter the temple... But, if you believe what I'm saying, you should head to Kakariko Village... Do you understand, Link?

Sheik (In front of Forest Temple):

The flow of time is always cruel... Its speed seems different for each person, but no one can change it... A thing that doesn't change with time is a memory of younger days... In order to come back here again, play the Minuet of Forest. (learn Minuet of Forest) Link... I'll see you again...

Sheik, meeting Link again in the Temple of Time:

You destroyed the wicked creatures that haunted the temple and awakened the Sage... But there are still other Sages who need your help. In order to awaken all the other Sages, you must become even more powerful. You must travel over mountains... under water... and even through time... If you want to return to your original time, return the Master Sword to the Pedestal of Time. By doing this, you will travel back in time seven years... The time will come when you will have to return here quickly... I will teach this to you for when that time comes... The song to return you to the Temple of Time... The Prelude of Light... (learn the song) As long as you hold the Ocarina of Time and the Master Sword, you hold time itself in your hands... Link, we shall meet again!

Sheik, in Death Mountain Crater:

It is something that grows over time... a true friendship. A feeling in the heart that becomes stronger over time... The passion of friendship will soon blossom into a righteous power and through it, you will know which way to go... This song is dedicated to the power of the heart... Listen to the Bolero of Fire... (learn song) Link... I'll see you again...

Sheik, in Ice Cavern:

We meet again, Link... If you came here to meet the Zoras, you wasted your time... This is all there is... With one exception, the Zoras are all now sealed under this thick ice sheet... I managed to rescue the Zora princess from under the ice, but... she left to head for the Water Temple... This ice is created by an evil curse... The monster in the Water Temple is the source of the curse. Unless you shut off the source, this ice will never melt.... If you have courage enough to confront the danger and save the Zoras, I will teach you the melody that leads to the temple. Time passes, people move.... Like a river's flow, it never ends... A childish mind will turn to noble ambition... Young love will become deep affection... The clear water's surface reflects growth... Now listen to the Serenade of Water to reflect upon yourself.... (learn Serenade of Water) Link... I'll see you again...

Sheik, after Link beats the Water Temple:

As the water rises, the evil is vanishing from the lake... Link, you did it! (Link warps in) Did Ruto want to thank me? I see... We have to return peace to Hyrule for her sake, too. Don't we? Look at that, Link... Together, you and Princess Ruto destroyed the evil monster! Once again, the lake is filled with pure water. All is as it was here.

Sheik, in Kakariko Village:

Get back, Link! (Sheik and Link get attacked by a swarm of darkness) Looks like you're coming around... Link... A terrible thing has happened! The evil shadow spirit has been released! Impa, the leader of Kakariko Village, had sealed the evil shadow spirit in the bottom of the well.... But the force of the evil spirit got so strong, the seal of the well broke, and it escaped into the world!! I believe Impa has gone to the Shadow Temple to seal it up again, but...she will be in danger without any help! Link! Impa is one of the six Sages. Destroy the evil shadow spirit and save Impa! There is an entrance to the Shadow Temple beneath the graveyard behind this village. The only thing I can do for you is teach you the melody that will lead you to the Shadow Temple... This is the melody that will draw you into the infinite darkness that absorbs even time... Listen to this, the Nocturne of Shadow!! (learn the Nocturne of Shadow) Let me take care of the village! I'm counting on you, Link!

Sheik, in front of the Spirit Temple:

(owl flies overhead) Past, present, future... The Master Sword is a ship with which you can sail upstream and downstream through time's river... The port for that ship is in the Temple of Time... To restore the Desert Colossus and enter the Spirit Temple, you must travel back through time's flow... Listen to this Requiem of Spirit... This melody will lead a child back to the desert. (learn Requiem of Spirit while owl looks on, owl flies away)

Sheik/Zelda in the Temple of Time:

I have been waiting for you, Link. Link, the Hero of Time... You have overcome many hardships and awakened six Sages. And now you have a final challenge, a showdown with Ganondorf, the King of Evil.... Before that... I have things I want to tell only to you. Please listen. Another unknown legend of the Triforce passed down by the shadow folk, the Sheikahs.... (cut scene) (centered) If you would seek the sacred triangle, listen well... The resting place of the sacred triangle, the Sacred Realm, is a mirror that reflects what is in the heart... the heart of one who enters it... If an evil heart, the Realm will become full of evil; if pure, the Realm will become a paradise. The Triforce...the sacred triangle... it is a balance that weighs the three forces: Power, Wisdom and Courage. If the heart of the one who holds the sacred triangle has all three forces in balance, that one will gain the True Force to govern all. But, if that one's heart is not in balance, the Triforce will separate into three parts: Power, Wisdom and Courage. Only one part will remain for the one who touched the Triforce...the part representing the force that one most believes in. If that one seeks the True Force, that one must acquire the two lost parts. Those two parts will be held within others chosen by destiny, who will bear the Triforce mark on the backs of their hands. (end cut scene) Seven years ago, Ganondorf, the King of Thieves, used the door you opened in the Temple of Time and entered the Sacred Realm. But when he laid his hands on the Triforce, the legend came true. The Triforce separated into three parts. Only the Triforce of Power remained in Ganondorf's hand. The strength of the Triforce of Power enabled him to become a mighty, evil king, but his dark ambitions were not satisfied. To gain complete mastery of the world, Ganondorf started looking for those chosen by destiny to hold the two other Triforce parts. The one who holds the Triforce of Courage is... You, Link! And the other, who holds the Triforce of Wisdom... is the seventh Sage, who is destined to be the leader of them all... (Sheik reveals himself as Zelda) It is I, the Princess of Hyrule, Zelda. I apologize for meeting you in disguise, but it was necessary to hide from the King of Evil. Please forgive me... On that day, seven years ago, Ganondorf attacked Hyrule Castle. (flashback) I saw you as I was escaping from the castle with my attendant, Impa. I thought I should entrust the Ocarina to you... I thought that would be our best chance... (end flashback) As long as you had the Ocarina in your possession, I thought Ganondorf could never enter the Sacred Realm, but... something I could never expect happened... After you opened the Door of Time, the Master Sword sealed you away in the Sacred Realm... Your spirit remained in the Sacred Realm...and then the Triforce fell into Ganondorf's hands. He went on to invade the Sacred Realm... Ganondorf had become the Evil King, and the Sacred Realm became a world of evil. All of this is an unfortunate coincidence. I passed myself off as a Sheikah and hoped that you would return. I waited for seven years... And...now you are back. The dark age ruled by Ganondorf the Evil King will end! The six Sages will open the sealed door and lure Ganondorf back into the Sacred Realm. I will then seal the door to the Sacred Realm from this world. Thus, Ganondorf the Evil King will vanish from Hyrule. Link... In order to do this, I need your courage again. Please protect me while I do my part. And here is a weapon that can penetrate the Evil King's defenses... The power given to the chosen ones... (centered) The sacred Arrow of Light!!! (You got the Light Arrow! The light of justice will smite evil!) (A great rumbling fills the room) That rumbling...It can't be!?

Super Smash Bros.
In Super Smash Bros. Melee Zelda has the option of transforming into Sheik. To do this, you must press down the analog stick with the B button. Sheik has a completely different moveset than Zelda. Sheik's moves and weapons are quick and similar to those of a ninja. Sheik is an extremely speedy character and for this reason she could be a bit difficult to control. Although she has an original moveset, she is found to have similarities with Captain Falcon. In Melee the two of them have a more powerful star rod attack. In the game, Sheik is always referred to as a female.

Sheik has been confirmed for the sequel to Super Smash Bros. Melee, Super Smash Bros. Brawl. Although she did not appear in The Legend of Zelda: Twilight Princess, the character model was based on a design drafted during the game's development. She has mostly the same moveset from Melee, and shares a Final Smash with Zelda, the Light Arrows.