In a lost age, the world is divided into four nations: the Water Tribes, the Earth Kingdom, the Fire Nation, and the Air Nomads. Within each nation, there is a remarkable order of men and women called the "benders" who can learn to harness their inborn talent and manipulate their native element. Bending is a powerful form combining martial art and elemental magic.

In each generation, only one bender is solely capable of controlling all four elements. That bender is the Avatar. The Avatar is the spirit of the world manifests in human form. When the Avatar dies, it reincarnates into the next nation in the cycle. Starting with the mastery of his or her native element, the Avatar learns to bend all four elements. Throughout the ages, the countless incarnations of the Avatar have served to keep the four nations in harmony.

Then, the firebenders attacked. Just as the world needed the Avatar the most, he mysteriously vanished. A hundred years later, the Fire Nation is near final victory in its ruthless war of world domination. The Air Nomads were destroyed, the Air Temples ravished, and all airbender monks eradicated. The Water Tribes were raided and driven to the brink of extinction. The Earth Kingdom remains and fights a hopeless war against the Fire Nation. Many believe the Avatar was never reborn into the Air Nomads and the cycle is broken.

In the desolated South Pole, a lone Water tribe struggles to survive. It is here that the village's last remaining waterbender Katara and her warrior brother Sokka rescue a strange 12-year-old boy named Aang who has been suspended in hibernation in an iceberg. The tribe soon discovers that Aang is not only an Airbender--the extinct race no one has seen in a century--but also the long lost Avatar. Now Katara and Sokka must safeguard the child Avatar in his journey to master all four elements and save the world from the Fire Nation.

Links from animea.com

Avatar: The Last Airbender episode 1: The Boy in the Iceberg

Avatar: The Last Airbender episode 2: The Avatar Returns

Avatar: The Last Airbender episode 3: The Southern Air Temple

Avatar: The Last Airbender episode 4: The Warriors of Kyoshi

Avatar: The Last Airbender episode 5: The King of Omashu

Avatar: The Last Airbender episode 6: Imprisoned

Avatar: The Last Airbender episode 7: Winter Solstice Part 1: The Spirit World

Avatar: The Last Airbender episode 8: Winter Solstice Part 2: Avatar Roku

Avatar: The Last Airbender episode 9: The Waterbending Scroll

Avatar: The Last Airbender episode 10: Jet

Avatar: The Last Airbender episode 11: The Great Divide

Avatar: The Last Airbender episode 12: The Storm

Avatar: The Last Airbender episode 13: The Blue Spirit

Avatar: The Last Airbender episode 14: The Fortuneteller

Avatar: The Last Airbender episode 15: Bato of the Water Tribe

Avatar: The Last Airbender episode 16: The Deserter

Avatar: The Last Airbender episode 17: The Northern Air Temple

Avatar: The Last Airbender episode 18: The Waterbending Master

Avatar: The Last Airbender episode 19: The Siege of the North, Part 1

Avatar: The Last Airbender episode 20: The Siege of the North, Part 2

Avatar: The Last Airbender episode 21: The Avatar State

Avatar: The Last Airbender episode 22: The Cave of Two Lovers

Avatar: The Last Airbender episode 23: Return to Omashu

Avatar: The Last Airbender episode 24: The Swamp

Avatar: The Last Airbender episode 25: Avatar Day

Avatar: The Last Airbender episode 26: The Blind Bandit

Avatar: The Last Airbender episode 27: Zuko Alone

Avatar: The Last Airbender episode 28: The Chase

Avatar: The Last Airbender episode 29: Bitter Work

Avatar: The Last Airbender episode 30: The Libary

Avatar: The Last Airbender episode 31: The Desert

Avatar: The Last Airbender episode 32: Journery to Ba Sing Se Part 1: The Serpent's Pass

Avatar: The Last Airbender episode 33: Journery to Ba Sing Se Part 2: The Drill

Avatar: The Last Airbender episode 34: City of Walls and Secrets

Avatar: The Last Airbender episode 35: Tales of Ba Sing Se

Avatar: The Last Airbender episode 36: Appa's Lost Days

Avatar: The Last Airbender episode 37: Lake Laogai

Avatar: The Last Airbender episode 38: The Earth King

Avatar: The Last Airbender episode 39: The Guru

Avatar: The Last Airbender episode 40: The Crossroads of Destiny

Avatar: The Last Airbender episode 41: Awakening

Avatar: The Last Airbender episode 42: The Headband

Avatar: The Last Airbender episode 43: The Painted Lady

Avatar: The Last Airbender episode 44: Sokka's Master

Avatar: The Last Airbender episode 45: The Beach

Avatar: The Last Airbender episode 46: The Avatar and the Firelord

Avatar: The Last Airbender episode 47: The Runaway

Avatar: The Last Airbender episode 48: The Puppetmaster

Avatar: The Last Airbender episode 49: Nightmares and Daydreams

Avatar: The Last Airbender episode 50: The Day of Black Sun Part 1: The Invasion

Avatar: The Last Airbender episode 51: The Day Of Black Sun Part 2: The Eclipse

Avatar: The Last Airbender episode 52: The Weastern Air Temple

Avatar: The Last Airbender episode 53: The Firebending Masters

Avatar: The Last Airbender episode 54: The Boiling Rock Part 1

Avatar: The Last Airbender episode 55: The Boiling Rock Part 2

Avatar: The Last Airbender episode 56: The Southern Raiders

Avatar: The Last Airbender episode 57: The Ember Island Players

Avatar: The Last Airbender episode 58: Sozin's Comet Part 1: The Pheonix King

Avatar: The Last Airbender episode 59: Sozin's Comet Part 1: The Pheonix King

Avatar: The Last Airbender episode 60: Sozin's Comet, Part 3: Into the InfernoAir

Avatar: The Last Airbender episode 61: Sozin's Comet, Part 4: Avatar Aang