"As we, her family, as well as her extended family of fans around the world so believe, Carrie's Princess Leia is forever entrenched in the franchise and her indelible presence is fundamental to the film".
"It's bittersweet facing my final chapter without her", Hamill wrote of Fisher in his tweet.
'She is simply irreplaceable.
Hamill also said Fisher "would love the worldwide outpouring of affection" that greeted the news she would appear in Episode IX.
Filmmaker JJ Abrams said last week that Fisher would be in the next Star Wars film to give the latest trilogy a "satisfying conclusion". They made clear it would come to fruition through some unused footage Abrams shot for The Force Awakens rather than recast or make a full CGI recreation of the actress.
Star Wars: Episode IX will begin filming at London's Pinewood Studios on August 1 with returning to direct the final installment of the Skywalker saga.
It was announced last week that the upcoming Star Wars: Episode IX - due to hit theaters in December 2019 - would repurpose unseen footage of Carrie Fisher to include her in the film as the iconic Leia. Add Star Wars as an interest to stay up to date on the latest Star Wars news, video, and analysis from ABC News.
Smoking ban in all public housing takes effect nationwide
Not to mention, they estimate it will save public housing agencies $153 million in costs related to healthcare and repairs. Housing authorities, including Memphis, have said they have met with tenants and will work with people to kick the habit.
Like Hamill himself, Fisher will get to complete her role in the Skywalker Saga all by herself.
A younger version of Lando was played by Donald Glover in Solo: A Star Wars Story. Legendary composer John Williams, who has been involved in every Star Wars film, will also return.
Hamill will return as Luke Skywalker, alongside cast members Daisy Ridley, Adam Driver, John Boyega, Oscar Isaac and Kelly Marie Tran.
Billy Dee Williams and Anthony Daniels are among the other Star Wars veterans who have been lined up to appear in Episode IX.
Join host and the voice of the Resistance Jessica Chobot as she takes us through an intriguing subplot that was left out of The Force Awakens.