A Protagonist Shall Lead Them

A Heroic Archetype of a character, frequently a Chosen One who rises out of adversity to unite and lead his people. The people in question also tend to be threatened; by disunity, by the Big Bad, by being a dying civilization, or other variations on the theme "their hour of greatest need". Through the leadership of the hero, the people see a considerable boost in quality of life and a renewed sense of pride and masses will flock to his banner.

In a sense, this is a much older interpretation of the Messianic Archetype - you could call this the Destined Leader Archetype. Before Christianity came along and gave us what most westerners understand as the Messiah with love and self-sacrifice, the Jewish people understood Messiah to mean "someone who will come in our time of need and unite the tribes of Israel" (because that's what the Bible said he would be). It's not impossible or unheard of for the two to overlap.

Older Than Feudalism. May overlap with The Paragon. If the people are pressed by a foreign power, the heroic leader may become part of La Résistance. His story will frequently include an Awesome Moment of Crowning. When a secondary hero rather than the protagonist is the leader, its a Supporting Leader.

Sister Trope to Rightful King Returns and Offered the Crown; this trope is not exclusive to lost royalty, nor will the protagonist always gain an official title afterwards. Very often also a Magnetic Hero.

Anime and Manga

 * Jotaro Kujo is set up to be this at the beginning of the third part of JoJo's Bizarre Adventure, "Stardust Crusaders." His Stand, Star Platinum, is named after the Tarot card "The Star" which stands for hope and salvation, and this is very fitting. At the end of the story, Jotaro is the only one able to beat Dio since
 * Usagi of Sailor Moon will become this in 1000 years when she becomes Neo-Queen Serenity.
 * Youko of The Twelve Kingdoms is thrust into this, at first unwillingly. All the emperors of the world are chosen by the kirin and without a ruler the kingdom falls into chaos. Some sucessions are more smooth than others though, and Youko had to be sought out in "our" world by Keiki.
 * Initially, Kenji of 20th Century Boys is set up to be this.
 * Simon in Tengen Toppa Gurren Lagann.
 * Hakuoro in Utawarerumono.
 * Kimba from Kimba the White Lion becomes the king of the jungle at a young age at the start of the series.

Film

 * Neo, "The One" of The Matrix is a weaker example than you might think originally (based on details from the 2nd film). He is a prophesied savior whose "return" raised morale and inspired humanity in their fight for survival, but he is not actually the leader of Zion nor does he hold any actual formal authority. In fact, he's overridden (and outranked) by individual captains on a few occasions.
 * Jake Sully in Avatar.
 * William Wallace in Braveheart.

Literature

 * Aragorn from The Lord of the Rings
 * The Pevensies and later Prince Caspian in The Chronicles of Narnia
 * King Arthur
 * Paul Atreides in Dune.
 * Referenced in an Isaac Asimov story, "Robot Dreams", where a robot has this kind of messianic dreams (complete with references to the story of Moses). Susan Calvin shoots him in the head.
 * In The Wheel of Time, a good chunk of the prophecies surrounding The Dragon Reborn and Rand Al'Thor talks about this kind of stuff.
 * Eragon from The Inheritance Cycle fits the "leader of La Résistance" type. His cousin Roran does this on a smaller scale, literally leading his village out of the Empire.
 * Bastian from The Neverending Story.
 * Arren/Lebannen from the Earthsea novel The Farthest Shore
 * Belgarion, when he becomes Overlord of the West in The Belgariad.
 * In Sax Rohmer's The Mask of Fu Manchu the eponymous Yellow Peril villain seeks to pass himself off as the prophesied "Masked Prophet" who will unite all Asiatic peoples (Arabs, Chinese, Japanese, Burmese, etc.) against the hated white race. This may have been suggested to Rohmer by the general British understanding of the Islamic idea of the Mahdi, which became widespread in Rohmer's boyhood.
 * Played with in Lawrence Watt-Evans' Touched by the Gods: Malledd is chosen by the gods to lead his people, but nobody, including Malledd, knows he's the Chosen One. He ends up.
 * Hazel-rah in Watership Down.

Live Action TV

 * Locke in Lost gets this down pat: He comes to lead after . Except
 * Jack ultimately volunteers himself to
 * Doctor Who: Harriet Jones, prime minister. Though she's only "chosen" by the fact that The Doctor knows 21st Century British future-history, she was credited in that history with stepping from the ashes of The Christmas Invasion and bringing Brittan through a golden age.
 * Pres. Laura Roslin from Battlestar Galactica.
 * Sheridan from Babylon 5 leads the fight both against the corrupt President Clarke, and also the Shadows and the Vorlons.

Religion and Mythology

 * Many in the Hebrew scriptures:
 * Moses
 * King Saul and his successors David and Solomon.
 * The Macabees.
 * Jesus in the New Testament, who gathers a lot of followers and was/is often called a king. If the Book of Revelation is any indication...
 * Speaking of scriptures, this trope is also present in Islam: Muhammad (PBUH) was the Amirul Mukminin, the Leader of the Faithful (the Muslims). He led the diverse people of Madinah (Muslims, Christians, Jews, Zoroastrians, pagans, etc) to take back the city of Makkah. After his death, this role is continued by the four Khulafaur Rasyidin (Four God-Guided Caliph). In fact, "Caliph" means successor to Muhammad's leadership. Some Muslims also believe that nearing the end of the world, this trope will come in full effect with the coming of Imam Mahdi (basically, a Messiah).

Video Games

 * Brutal Legend: "To summon a warrior into this world who would lead our armies to BRUTAL VICTORY. It was made for a god, not for you... not for... a ROADIE..." Good thing Eddie Riggs has The Power of Rock.
 * Thrall is this for the Horde in Warcraft III and World of Warcraft.
 * Mega Man X ends up in this role as of Mega Man Zero. Unfortunately, being near-immortal and fighting the never-ending battle with no help pretty much tore his psyche up, making up half of his motivation for a Heroic Sacrifice. His replacement then helps steer everything into hell.
 * The Nerevarine from The Elder Scrolls fits both this and Messianic Archetype pretty well. His background and predicted traits fit right in with the Jewish messiah, and the way s/he turns out to be is more like the Christian notion (i.e., didn't come to wipe out all the occupying foreigners and restore ethnic purity after all).
 * Shepard of Mass Effect is another combination of this trope and Messianic Archetype. Of course, the definition of who exactly s/he is defending varies with Paragon and Renegade.
 * A main quest in Guild Wars in actually named "And a Hero shall lead them". The whole point of the Nightfall campaign (and the other to a lesser extent) is the hero (i.e. the player) leading others to save the day.
 * In many a 4X games, this is generally you. A God Is You.

Western Animation

 * Aang of Avatar: The Last Airbender. All Avatars have this, as it is their job to 'keep the balance of the world', but Aang in particular as he must end 100 years of war.
 * Interestingly, he might not be the most straight example, despite being a prime contender. Sokka seems to do a lot more of the day to day leading, being the strategist of the group, while Aang would much prefer to go around and play. (Although, Sokka does let Aang make choices on Avatar matters). By the end of the series
 * Dreamy Smurf in The Smurfs who dreams of being taken to the land of the Pookies where his Second Coming portends a deliverance from the tyrannical Norf Nags.