The Bourne Identity actor and friend Ben Affleck launched their careers with 1997 movie Good Will Hunting - which they wrote and starred in - and he doesn't think he would have enjoyed the life he has since then if the late actor hadn't agreed to take on a starring role.
He said: "Ben (Affleck) and I owe everything to him. He said yes to our movie and he got it made. I could never thank him enough. I look around at the life I have and how blessed I feel and so much of it started with him."
The 43-year-old actor was "shocked" when Robin, 63, committed suicide last month and hopes the tragedy will raise awareness of depression and how debilitating it can be.
Robin Williams in Good Will Hunting.