Born more than six decades before the Battle of Yavin, on Coruscant, to diplomats from Corellia, Gallia first had experience with the Jedi when her parents went to negotiations at Lannik. While there, the Red laro launched an attack. Adi's life was saved by Lannik Jedi Even Piell. Gallia felt a debt of gratitude to the diminutive Jedi, and it inspired her to become a Jedi herself, after it was discovered she was Force-sensitive.
Eventually, Adi earned a seat on the Jedi Council by 42 BBY. She was the first to hear of the Trade Federation's suspicious movements in the outlying regions through her carefully cultivated network of contacts. Having close ties to Supreme Chancellor Finis Valorum, she informed him of her findings, and Jedi Master Qui-Gon Jinn and his Padawan Obi-Wan Kenobi were sent to deal with the blockade around Naboo.
As a Council member, Adi Gallia succeeded in many assignments, including those undertaken during the Stark Hyperspace War. Adi and her Padawan Siri Tachi went on many missions with Adi's close friend Qui-Gon Jinn and his apprentice Obi-Wan Kenobi. On their first mission together, the two pairs of Jedi traveled to the world of Kegan where they were tasked to recover a Force-sensitive baby girl. Though they initially received difficulty, Adi and Qui-Gon, along with their apprentices, managed to pull off the mission. Gallia and Siri would then team up with Obi-Wan to rescue Qui-Gon when the Jedi Master was captured by the insane scientist Jenna Zan Arbor.
On one of their last missions together before Qui-Gon's death, they had to protect a boy named Talesan Fry who had overheard a plot against twenty senators. The Jedi succeeded and saved Fry, but during the mission Siri and Obi-Wan fell in love, despite the Jedi Code that forbade attachments. Adi did not realize this, but Qui-Gon did. He, however, decided not to tell her.
After the Battle of Naboo, Adi Gallia traveled with fellow Council members Mace Windu, Even Piell, Ki-Adi Mundi, Plo Koon, Yaddle and Ki-Adi-Mundi's Padawan A'Sharad Hett to Malastare to supervise a peace treaty between warring factions. Upon arriving at the meeting between the Lannik Prince R'cardo Sooflie IX and the Red laro, R'cardo enraged Adi, who declared that she was here to finish her parents' work. After the first part of the negotiations finished the Jedi were offered a lift to their quarters by the Lannik advisor Hutar Zash. They were betrayed by Hurtar and the Lannik bodyguards attempted to kill all the Jedi. Even Piell sliced the speeder in half causing himself, Adi, and Mace Windu to fall into a podrace below. They were rescued by the other Jedi and speculated that the Red Iaro were going to kill the Prince and hurried to his building. However, when they arrived the terrorists had set Akk dogs on R'cardo. Gallia was attacked by one but was saved by Yaddle who stabbed the beast in the eye. Mace Windu befriended the other through the force and brought the negotiations to an end, but succeeding in the mission.
In 30 BBY, Adi Gallia was sent with Ki-Adi-Mundi and A'Sharad Helt to track down the deadly bounty huter Aurra Sing, an infamous killer of many Jedi. Piloting a Consular-class pace cruiser, they eventually found her in the Kamdon system. They were nearly killed in a space battle with the assassin, but were able to eject in an escape pod.
The three Jedi were taken in by a nearby Quarren ship, which Senator Tikkes was onboard. The ship landed on a planet in the Kamdon system, following Aurra Sing. Tikkes's scientists investigated the planet, most getting caught up in rope traps or mines. They spotted An'ya Kuro and, assuming she was the one behind it, shot her. With that, Aurra Sing appeared on her speeder bike.
Tikkes ordered his men to kill her, but, after blocking some blaster bolts with her lightsaber, Adi called upon the Force to throw a large bolder at Sing. Ki-Adi, unsure that Sing was dead, sent Adi Gallia to reassure. Just as Ki had suspected, Sing survived, and escaped. As Adi was searching around, she found a case, and decided the case probably belonged to Sing and was of great importance to her. So she decided to open the case and discovered that the stories were true, Sing had killed Jedi and realized that she was heading for Senator Tikkes, and Padawan Hett was the only one standing in her way. Adi started to head to Tikkes ship, but in doing so, stepped on one of Sing's planted mines. Gallia survived, and Aurra Sing was defeated by A'Sharad, though she managed to escape once again.
Just before the Battle of Geonosis, Adi was to test a new Jedi starship, Delta-7 Aethersprite. During the training exercises, she was sent to help a Feeorin called Nym in the Karthakk system. During these missions, Gallia helped destroy the Hex factory producing the deadly tritexalon poison for Cavik Toth. With the assistance of her former apprentice Siri Tachi, she also destroyed Toth's Hex equipped fleet before it could reach Geonosis. Undoubtedly, Gallia's actions prevented the death of many clone troopers and Jedi. Also, Adi Gallia helped provide air cover for Republic ships descending to Geonosis. Her next mission was with Siri Tachi, A'Sharad Hett, and other members of a Jedi strike team sent to rescue Obi-Wan Kenobi, his apprentice Anakin Skywalker and Senator Padme Amidala from the Separatist leaders. They participated in the air assault and succeeded. That was the beginning of the Clone Wars. During the war, Gallia engaged Separatist forces on the planet of Agamar.
Adi Gallia continued her service to the Jedi Council and the Republic during the Clone Wars. She met for many council meetings including the meeting where the council discussed what their plan was for destroying General Grievous. Adi suggested that the council promote more Padawans to Jedi Knights. The council agreed to her idea. With Ki-Adi-Mundi, Anakin Skywalker, and Plo Koon, she helped save Obi-Wan Kenobi and the ARC trooper Alpha-17 from their refuge after escaping the clutches of Asajj Ventress. Adi led the Republic forces to victory during the Battle o Agamar.
At some point during the war, General Grievous had captured Master Eeth Koth. Grievous, proud of his capture of Master Koth, sent a message to the Jedi Council daring the Jedi to find their comrade, and Adi, along with Anakin Skywalker and Obi-Wan Kenobi, volunteered to lead the rescue mission. After Obi-Wan discovered and interpreted a hidden signal revealing Koth's position that the captured Council Member had left, the three Jedi discovered that Koth was being held on Saleucami. Gallia was initially confused on whether or not it was an accurate report, given that Republic Intelligence had not specified the planet as one controlled by Grievous.
However, Republic Intelligence proved inaccurate and the three Jedi led Republic forces to the planet where they engaged Grievous's fleet in battle. The objective- capture Grievous and save Eeth Koth. As Kenobi lured Grievous onto his vessel over Saleucami, Gallia and Skywalker rushed the bridge of Grievous' flagship, confronting a host of commando droids. Despite the droids' best attempts to halt the two Jedi, Koth was successfully freed.
Later on in the skirmish, as Koth was being escorted back to a Republic vessel, Kenobi reported that Grievous had defeated him and escaped. Gallia left Skywalker and Koth in order to find and help Kenobi flank Grievous and capture him once and for all. Meanwhile Kenobi was engaging Grievous. Grievous managed to get the upper hand but became unsuccessful and fell into a docking tube. Kenobi managed to get a grip and was about to be killed by Grievous but Gallia then arrived and engaged Grievous in a fierce battle. The fight stopped short though due to the distraction of the docking tube being ruptured, allowing Grievous to flee to an escape pod and, from there, the surface of the planet.
After Obi-Wan Kenobi and Anakin Skywalker discovered the survival of Asajj Ventress and the location of a Separatist base on Boz Pity, Mace Windu dispatched a group of Jedi led by himself to capture multiple key Separatist leaders- and Adi Gallia was selected as a member of the team. During the Battle of Boz Pity, Adi confronted General Grievous again while directing her troops as a General alongside Mace Windu.
Gallia engaged Grievous in combat, but the cyborg general used his extra arms to surprise the Jedi Master. He grabbed her neck, then plunged two lightsabers into her chest before dropping her lifeless body to the ground.
Mace Windu witnessed Gallia's murder and attempted to avenge her, though Grievous managed to escape before he was eventually hunted down and killed by Adi's old friend, Obi-Wan. Her place on the council was filled by her niece, Stass Allie, until the execution of Order 66 in 19 BBY where she was murdered on Saleucami. In honor of his fallen friend, the pirate Nym named a volcano on the planet of Lok, Adi's Rest.
In the Star Wars canon continuity however, this is retconned. In the Star Wars The Clone Wars television show, Adi Gallia and fellow Jedi Master Obi-Wan Kenobi embark on a mission to hunt down the monstrous nightbrother Savage Opress and his former Sith Lord brother Darth Maul. Their mission leads them to Florrum, where Maul and Opress had taken over a segment of Hondo Ohnaka's pirate crew and were launching a mission to take over Florrum. Gallia and Kenobi engaged the 2 Nightbrothers in a ferocious duel, but Gallia was headbutted and impaled with a lightsaber by Savage.