According to People Magazine, Maynard posted a goodbye message to Facebook before taking her life on Saturday.
"Goodbye to all my dear friends and family that I love," she wrote. "Today is the day I have chosen to pass away with dignity in the face of my terminal illness, this terrible brain cancer that has taken so much from me ... but would have taken so much more. The world is a beautiful place, travel has been my greatest teacher, my close friends and folks are the greatest givers. I even have a ring of support around my bed as I type ... Goodbye world. Spread good energy. Pay it forward!"
Earlier this year, Maynard was given just months to live after being diagnosed with glioblastoma, the deadliest form of brain cancer. Maynard left her home in the San Francisco Bay Area and moved to Oregon to take advantage of that state's Death with Dignity Act, which allows terminally ill patients to end their own lives with a lethal dose of medication prescribed to them by a doctor.
"We all just realized that I am terminally ill and I'm dying and I would just prefer to die with less pain and less suffering," Maynard told ABC in an interview last month.
Maynard had previously stated that she planned to end her life on Nov. 1, but in later statements, including a video posted last week, said she had not yet made a final decision on when she would take the lethal dose of medication.
Tap to see video if viewing on News app.
Compassion & Choices, the right-to-die advocacy group Maynard had been working with, confirmed Sunday evening that Maynard ended her life on Nov. 1.
"Brittany suffered increasingly frequent and longer seizures, severe head and neck pain, and stroke-like symptoms," the statement said. "As symptoms grew more severe she chose to abbreviate the dying process by taking the aid-in-dying medication she had received months ago."
An obituary has been posted on Maynard's website.
According to Compassion & Choices, Maynard passed away in her home peacefully, surrounded by friends and family.
More than 750 people in Oregon used the law to die as of Dec. 31, 2013, according to the Associated Press. The median age of the deceased is 71. Only six were younger than 35, like Maynard.