Hamill, 65, who played Luke Skywalker, the brother to Fisher's iconic character Leia, wrote a lengthy Twitter post with the caption, "#AFewWords."
"It's never easy to lose such a vital, irreplaceable member of the family, but this is downright heartbreaking," he wrote. "Carrie was one-of-a-kind who belonged to us all - whether she liked it or not. She was OUR Princess, damn it, & the actress who played her blurred into one gorgeous, fiercely independent & ferociously funny, take-charge woman who took our collective breath away."
Hamill added that her "vulnerability" made fans and friends root for her on and off-screen.
"She played such a crucial role in my professional & personal life, & both would have been far emptier without her. I am grateful for the laughter, the wisdom, the kindness & even the bratty, self-indulgent crap my beloved space-twin game me through the years. Thanks Carrie, I love you," he closed.
A family spokesman, Simon Halls, confirmed the actress' death Tuesday morning.
"It is with a very deep sadness that Billie Lourd confirms that her beloved mother, Carrie Fisher, passed away at 8:55 this morning," the rep said in a statement to ABC News.
Hamill wasn't the only "Star Wars" actor to remember Fisher.
Jeremy Bulloch, 71, the actor best known for playing the fearsome bounty hunter Boba Fett, tells ABC News he was devastated to learn of Fisher's death.
She was "just a diamond," he said.
"Funnily enough, I saw more of Carrie when we were at Disneyland...while they were having a Disney Weekend with 'Star Wars.' With her there, it was terribly difficult, because she was cracking jokes...you have Carrie just shrieking with laughter," he added. "You can't say any more ... she was just brilliant."
Chewbacca actor Peter Mayhew, 72, told ABC News affiliate WFAA in Texas of his on-screen reunion with Fisher in last year's "The Force Awakens."
"That was probably the last screen embrace that we did. She brought her character back, and in the last one, she was an older person. Therefore, she was wiser," he said. "She was a person that was a true princess."
These new tributes add to the hundreds that poured in Tuesday from co-stars and fans.
Bob Iger, the chairman and CEO of The Walt Disney Co., said, "Carrie Fisher was one of a kind, a true character who shared her talent and her truth with us all with her trademark wit and irreverence. Millions fell in love with her as the indomitable Princess Leia; she will always have a special place in the hearts of 'Star Wars' fans as well as all of us who were lucky enough to know her personally."
Fisher is survived by her 24-year-old daughter Billie Lourd.
Lucasfilm and ABC News are both owned by The Walt Disney Co.