Mothma was born into a wealthy, influential family on Chandrila. Her mother was the governor of the planet, and her father was an arbiter-general for the Republic. At the age of 21 (27 BBY) she was elected to represent the Bormea Sector in the Galactic Senate, becoming the youngest Senator ever to serve—a record later broken by Leia Organa Solo, future apprentice and colleague of Mothma.

To those who knew her, Mothma was kind and caring, yet sometimes forgot herself when dealing in politics, which often seemed to claim importance over everything else in her life. She was a daring woman with charisma and political savvy, but she was not devoid of enemies.

"That is our goal: To become the New Republic in fact as well as name."
―Mon Mothma

"We are not Separatists trying to leave the Republic, we are Loyalists trying to preserve democracy in the Republic."
―Mon Mothma

her death:

Mothma supported Luke Skywalker in his efforts to reestablish the Jedi Order to protect and guide the New Republic. She gave her official sanction to Skywalker's efforts to find and recruit potential Jedi. Mothma also arranged for Skywalker to be given the former Rebel base on Yavin IV's moon as a home for the new Jedi school.

Unlike her years in the Alliance, Mothma did not stay hidden in safety. During a diplomatic visit to Coruscant, a Caridan ambassador threw what appeared to be a drink on Mothma's face as an insulting send-off gesture. This "drink" turned out to be nanomachines that slowly affected Mothma. Mothma decided to resign her post as Chief of State as her condition worsened, and guided the council to appoint Leia Organa Solo to succeed her in office. The condition nearly killed her, but at the last minute Mothma was saved by the Mon Calamari Jedi Cilghal who used the Force to cleanse her body.

Without the nano destroyers in her body, Mothma's condition improved. Within a few weeks she was standing again, something that Leia never thought she'd see Mothma do again. Leia tried to convince Mothma to become Chief of State again, but Mothma refused—feeling that the time had come for her to step aside.

Despite her improvement, Mothma never completely recovered. For the most part, she retired from public life. However, in 17 ABY, during the Almanian Uprising, she became acting Chief of State while Leia Organa Solo, the current Chief of State, led Wedge Antilles and a fleet to Almania to find her brother, and rescue him from the megalomaniac Kueller. She later resigned when Leia returned.

In 19 ABY, she was present at the signing of the Bastion Accords, and was a guest of honor at the wedding of Luke Skywalker and Mara Jade. Her condition continued to worsen, albeit slowly, and shortly before the Yuuzhan Vong War she died quietly in her sleep. In honor of her courage and bravery throughout the years, an Imperial Star Destroyer was given the name Mon Mothma.