Alderaan, a terrestrial planet abundant with mountains, resided within the Core Worlds. During the concluding decades of the Galactic Republic, it was governed by Queen Breha Organa, while her spouse, Senator Bail Prestor Organa, represented it in the Galactic Senate. Alderaan was celebrated for its serene atmosphere, scenic landscapes, and the refinement of its artistic and cultural expressions.
Following the rise of Sheev Palpatine's Galactic Empire, Alderaan became a key player in the formation of the Rebel Alliance, a movement dedicated to reinstating the values of the Old Republic, and was among the earliest to champion it. Due to its connections to the Alliance, the planet met its destruction when Grand Moff Wilhuff Tarkin chose to test the superlaser of the Death Star, a moon-sized battle station engineered by the Empire, at its maximum capacity. Princess Leia Organa, the adopted daughter of Bail and Breha Organa and the heir to the royal house of Alderaan, was among the few who survived this cataclysm.

Viewed from space, Alderaan, a planet situated in the star system bearing the same name, presented itself as a blue-green sphere enveloped by a network of white clouds. Its terrain featured extensive bodies of water and was adorned with snow-covered mountains, interspersed with verdant grassy hills. Throughout the galaxy, Alderaan was affectionately known as "the planet of beauty." The inhabitants of Alderaan, known as Alderaanians, possessed a deep appreciation for the arts and lived in pursuit of beauty, yet the planet also concealed treacherous cliffs and forgotten ravines. Noteworthy natural landmarks on Alderaan encompassed the Cloudshape Falls, the Glarus Lagoons, and the Isatabith rain forest.
Alderaan fostered the growth of various grapevines, which significantly contributed to the production of Toniray and emerald wine. The planet's native wildlife included creatures such as the Alderaanian wolf-cat, nerfs, and a species of white-winged bird.
The design of cities on Alderaan was meticulously executed to harmonize with the natural splendor of their surroundings. For instance, the palace of the royal family, a project spanning over a millennium, and the city that surrounded it seamlessly merged with the adjacent snow-capped peaks. Alderaanian architecture incorporated the use of white synthstone, which served as an inspiration for the architectural styles of certain mining economies within the Outer Rim Territories, such as the floating colony of Cloud City, as well as the planets Lothal and Garel.
Despite the lyrics of the traditional Alderaanian lullaby "Mirrorbright" alluding to a moon, the planet lacked any natural satellites.
Alderaan, a peaceful world, stood as one of the most tenured members of the Galactic Republic, the democratic alliance that presided over the majority of the galaxy, and it was among the original founding worlds. Upon the establishment of its monarchy, it was decreed that the designated heir to Alderaan must successfully complete a Challenge of the Heart, Challenge of the Mind and Challenge of the Body, which would be announced on their Day of Demand, and upon their successful completion, they would be officially invested as the heir. In antiquity, Alderaanian heirs participating in their Day of Demand were required to battle their way into the palace throne room. Prior to establishing a permanent base on Coruscant, the Jedi High Council maintained a council on Alderaan.
Yana Ro, anticipating her fondness for the world, expressed a desire to visit Alderaan following the Night of Sorrow and the definitive severance of her ties with the Path of the Open Hand cult. Ro conveyed this sentiment to Shea Ganandra, with whom she aspired to establish a hauling enterprise. During the High Republic Era, Alderaan flourished as a prosperous world and, as a signatory to the Republic Defense Coalition treaties, was obligated to provide starships and personnel to be commanded by Republic military officers during periods of crisis. Following the resolution of these crises, the ships and personnel were to be returned to Alderaan. Alderaan was summoned to fulfill this obligation circa 232 BBY, to assist the Republic in its conflict against the Nihil, a band of marauders responsible for the Great Hyperspace Disaster.
Sometime between 40 BBY and 28 BBY, Princess Breha Organa, the sixteen-year-old heir apparent of Alderaan, engaged in her Day of Demand, during which she proclaimed her challenges of the heart, mind, and body. However, during her Challenge of the Body, Breha fell from the renowned Alderaanian mountain Appenza Peak and would have perished were it not for the swift intervention of the guards observing from a distance. The princess survived but had to have her heart and lungs replaced with pulmonodes. After her fall Breha was officially invested as crown princess and heir to the throne of Alderaan. Years later the people would still speak of Breha's accident.
Breha Organa eventually succeeded her mother as queen of Alderaan.
By the time of the Invasion of Naboo, Alderaan had experienced peace for generations. Senator Bail Antilles represented the planet in the Galactic Senate. In that year, the then-Supreme Chancellor of the Republic, Finis Valorum, was removed from office, and Antilles was nominated for the position in the subsequent election. Nevertheless, Senator Sheev Palpatine, representing the sovereign system of Naboo, defeated the Alderaanian senator.
In 28 BBY, former queen of Naboo Senator Padmé Amidala and her entourage were invited to Alderaan by Queen Breha and stayed at the royal palace for a week before returning home to Naboo.
A decade later, Viceroy Bail Prestor Organa, the prince consort of Queen Breha Organa, the planet's ruler, represented Alderaan in the Senate. At that juncture, the Republic confronted a secessionist crisis stemming from the existence of the Confederacy of Independent Systems led by Count Dooku, which propelled the galaxy toward the brink of war. Through Organa, Alderaan held membership in Chancellor Palpatine's Loyalist Committee, which focused on ensuring the stability of the Republic amidst the Separatist crisis and would later endeavor to curtail Palpatine's increasing executive authority. In that year, an army of clones was discovered on the planet Kamino, which the Senate would appropriate to combat the Separatists. To safeguard the Republic from the looming threat, the Supreme Chancellor was granted emergency powers, a decision that ran counter to the pacifist principles of Alderaan and its representative, and which ultimately precipitated the outbreak of the Clone Wars. During the Clone Wars Viceroy Bail Organa became Alderaan's military leader.

At some point during the Clone Wars, Alderaan hosted an conference dedicated to assisting war refugees. Padmé Amidala, then senator of Naboo, narrowly escaped assassination during the conference when the Hutt crime lord Ziro, whom Amidala had imprisoned in prison, enlisted the services of the bounty hunter Aurra Sing for revenge. However, the Jedi apprentice Ahsoka Tano foiled the plot. Many refugees from all over the Republic came to stay on Alderaan during the war to find their way again or to stay.
Queen Breha and Viceroy Bail would send aid to worlds that had been ravaged by the Separatists, sending not just money and supplies but also doctors, teachers, architects, builders, medics, and droids.
Around the time of the Battle of Kadavo, two Alderaanian tourists visiting Tatooine died in a speeder-bike accident. The Zygerrian News implied that the two had gotten intoxicated in the cantina of Mos Eisley, which caused the accident.
The Clone Wars brought about a transformation on Alderaan. Despite remaining a peaceful planet devoid of substantial weaponry, the Royal Alderaan Civil Fleet possessed "more teeth," its officers had endured greater hardships, the planet produced more practical items in larger quantities, and its population quietly swelled due to the influx of refugees.
Following the conclusion of the Clone Wars, Viceroy Bail and Queen Breha adopted Leia Amidala Skywalker, the daughter of the now deceased Padmé Amidala and former Jedi Knight turned Sith Lord Anakin Skywalker, renaming her to Leia Organa and making her princess of Alderaan. Leia's adoption was announced on her Name Day three or four days after her birth and was publicly celebrated on Alderaan.

In 3 BBY, Leia Organa participated in her Day of Demand and after completing her three challenges became invested as crown princess and the future queen of Alderaan.
As the Clone Wars drew to a close, Chancellor Palpatine had dissolved the Republic, establishing the Galactic Empire in its place. However, a small contingent of systems rebelled against this new order, and the Alliance to Restore the Republic ultimately materialized through the efforts of Bail Organa and his former colleague in the Galactic Senate, Senator Mon Mothma of Chandrila. During this era, Alderaan served as the Alliance's primary supplier of munitions. Princess Leia Organa, the planet's crown princess and representative in the Imperial Senate, began to exploit her diplomatic immunity as an Imperial senator to execute Rebel missions within restricted Imperial systems.
During the Galactic Civil War, Alderaan was designated as an Alliance safe world. It was featured on a galactic map with a legend detailing the various Alliance safe worlds, starfighter hubs at level five or higher, rebel operations sectors and regional headquarters, and shadow planets with deep space caches. The map would later be incorporated into The Rebel Files.
Approximately three years prior to the Battle of Yavin, Senator Bail Organa dispatched three Sphyrna-class Hammerhead corvettes to the Phoenix Cell, which has sustained losses while fleeing Garel. Given Alderaan's inability to openly support the rebels, Senator Organa arranged for his adopted daughter Leia to deliver the vessels to Lothal. The Alderaanians risked losing their seat in the Imperial Senate among other Imperial sanctions. Senator Organa orchestrated for the crew of the Ghost to "steal" the ships from an Imperial depot on Lothal to absolve Alderaan of blame for the "theft." With the assistance of the crew of the Ghost and the former Governor Ryder Azadi, Leia successfully delivered the three Hammerhead corvettes to the Phoenix rebels following a skirmish at the Imperial depot.
In 1 BBY, shortly before the Battle of Scarif, and three weeks prior to the equinox festivities, Senator Bail Organa headed towards Alderaan to tell their people that there would "be no peace," after the plans for the Death Star, a planet-killing Imperial superlaser, were discovered. The plans were later stolen from the data vault on Scarif, and transferred aboard the Tantive IV. Princess Leia of Alderaan, Bail's adopted daughter and thus member of the Elder Houses was captured by the Imperial Navy while smuggling the plans to the Alliance base. Organa was taken prisoner by Vader, the Emperor's second-in-command, and brought before the Death Star's commanding officer, Grand Moff Wilhuff Tarkin.

Under threat of destroying her planet, Leia gave a fake location of the rebel base to Tarkin, only for Tarkin to nevertheless destroy Alderaan—noting that Dantooine was too remote for an "effective demonstration"—to punish the world for supporting the Rebellion, hoping the annihilation of the entire world would make the rest of the galaxy fear Imperial retribution for supporting the Rebels. The Imperials forced the princess to witness the obliteration of her home planet. The planet's destruction left only an asteroid field behind, which was blockaded by the Empire.
On Coruscant, the Empire's planetary capital, the numerous Alderaanian residents of Level 3204 began to hold vigils for those who had perished in what they called "the Disaster." However, as more information became available about the Empire's role in the destruction of Alderaan, the vigils soon turned into riots, which were quickly repressed by brute force. The Empire defended the destruction of the planet to its military, claiming that its population had chosen its destruction by supporting anarchy. A short time after Alderaan's destruction, the Death Star was destroyed in the Battle of Yavin, taking Tarkin and many other high ranking Imperials with it.
Under the orders of Vader, the Imperial Military was to "complete" the destruction of Alderaan by hunting any remaining Alderaanians. Almost immediately after the Death Star's destruction, Leia Organa would embark on a mission to rescue the survivors of Alderaan from Imperial reprisals. Also following the Battle of Yavin, Vader took the remains of Alderaan to serve as reminders to worlds that attempted to resist the Emperor; following an assassination attempt on himself at Shu-Torun, Vader then gave Trios, the new Queen of that planet, one of these reminders. Finding himself the last of House Glorio, Rabael Dir Glorio, who had also been 26th in line to the throne, tried to have his own revenge on the Empire but was left behind and for dead by a crew working for the Son-tuul Pride.
In 4 ABY, Leia married Han Solo on the forest moon of Endor. Due to the destruction of Alderaan Leia's mother, Breha Organa, couldn't attach the Rhindon Sword to her waist before Leia went to meet her husband though during the ceremony Leia felt as if her mother was attaching the sword and her father, Bail Organa, was kissing her on the cheek. After the ceremony, Leia mused to herself that had Alderaan not been destroyed she would have been married at the cathedral in Aldera, with a customary lace dress, an hour dedicated to the bell service, three different traditional meals with guests of rank and more.
By 5 ABY, a flotilla of starships orbited the Alderaanian Graveyard, the new name for the debris remaining of the planet. Princess Leia managed to use her political connections to take scrap from the Death Star, initially intended for incineration, to be used to construct a new space station around the planet.
By the time of the New Republic, Alderaan's destruction would become a stark reminder for future generations about the terrors of the Galactic Empire, and would often be an 'uncomfortable subject' for those that brought up the planet's destruction in conversation. As such, surviving Alderaanians would be treated with great respect for their lost world and people. For collectors, rare bottles of the alcoholic beverage Toniray would become a highly-prized commodity.

Alderaan was home to a population of humans, referred to as Alderaanians, who were celebrated for their pacifistic philosophy. Even amidst galactic conflicts, the Alderaanians eschewed weaponry. However, they were not devoid of courage, as many chose to join the rebellion against the Galactic Empire. Their society was governed by the House of Organa, in conjunction with an individual holding the titles of Viceroy and First Chairman. The female offspring of the royal couple was addressed as a princess. For diplomatic endeavors, the Royal Family utilized streamlined cruisers.
According to Nash Windrider, on Alderaan, its people were encouraged to learn and grow. All education was free, and people would volunteer to teach various skills or crafts just for fun. Queen Breha herself served as the minister of education, and personally mentored a select number of young Alderaanians, including Evaan Verlaine, teaching them about the culture and heritage of their homeworld.
Alderaan also had a number of traditions involving braids such as who wore them, when and why that varied from continent to continent and age to age. The Alderaaian monarch was expected to wear braids.
Every child of Alderaan owned a keepsake chest whose designs would be carved by the child's parents and grandparents though the child themselves choose what went inside. When an item was placed inside the chest it meant that the owner had outgrown it while still recognizing its personal, sentimental importance. In adulthood, an Alderaanian could then open their chest, look back, and see how they had chosen to tell their own story. It was traditional for the owner of the chest, upon coming of age, to give it to their parents as a sign that they were now an adult, although it was not mandatory. Many heirs of Alderaan would give up their keepsake chest before their investiture as crown prince or princess though the ritual didn't demand it.
Alderaan made its inaugural appearance in Star Wars: Episode IV A New Hope, the foundational film of the Star Wars saga. Within that movie, the planet was solely depicted from space during the scene illustrating its destruction. In the treatment, rough draft, second draft, and third draft of what would eventually become A New Hope, the name Alderaan was employed to designate the capital of the "New Galactic Empire." At that juncture, it was portrayed as a colossal gas planet resembling Bespin, complete with a city akin to Cloud City. In the second draft of A New Hope, the home planet of Princess Leia was called Ogana Major. Aquilae, Utapau, and Ophuchi were also considered as names for worlds partially corresponding to Alderaan.
Following the triumph of A New Hope, an extensive ancillary world was being developed around the movie. To ensure coherence, George Lucas opted to create a series of background narratives and concepts. Within these notes, Alderaan was described as an Earth-like planet, aged between four and five million years, adorned with towering snow-capped mountains and verdant pastures. The same notes also characterized the planet as the capital of its star system, possessing its own Senate. In canon, the surface of Alderaan only made its first appearance in the 2005 movie Star Wars: Episode III Revenge of the Sith. The planet's mountainous terrain was modeled after a location in the Swiss Alps.
In the 2018 reference book Star Wars: The Rebel Files, Alderaan was mistakenly depicted as being in the Colonies instead of the Core Worlds.