The actor, whose Star Wars character Luke Skywalker lost a hand in an epic light-sabre battle with nemesis Darth Vader, shared the message on social media on Monday where it has been viewed thousands of times.
Hamill says in the video: “Now kids, be yourself. You can do anything. There are no barriers you can’t break, no challenges you can’t overcome.
“Remember, Luke lost his hand to Vader, but that didn’t stop him from defeating the Empire.
“So have courage, be determined, and always remember that your limb difference is your very own superpower. And may The Force be with you all.”
The message has been viewed thousands of times on Twitter and YouTube.
One Twitter user wrote: “What a fantastic message and from a brilliant influential figure, who was dealing with a character with a prosthetic limb before it was even technically possible! Such a positive force!”
Another said: “This proves that Mr. @HamillHimself is just as much of a hero offscreen as he is on!
“Thanks for this sweet message to the super Younglings that get to be like the one and only #LukeSkywalker.”
One YouTube user wrote: “I am a 37 year old man and I have a 6 year old daughter with a limb difference. Thank you Mark.”
Open Bionics makes custom-built prosthetic limbs, or “hero arms”, for children and adults which are controlled by the user’s muscles.