Robert De Niro "can't imagine" life without Martin Scorsese.
The 76-year-old actor has been close friends with the filmmaker, 77, for more than 40 years, and has said their lifelong bond - which began when Robert starred in Martin's 1973 movie 'Mean Streets' - means a lot to him.
Robert explained: "I consider myself very lucky to have that long of a relationship with him. I can't imagine my life without it."
The pair have worked together on nine films, including their most recent collaboration 'The Irishman', which co-stars Al Pacino and Joe Pesci and is nominated for 10 Oscars and four Screen Actors Guild Awards.
And Robert says working on the Netflix movie was "special" for everyone involved, as he said Martin can be "very sensitive" about the stars he casts for his projects.
The 'Taxi Driver' star told People magazine: "Doing this film was so special for all of us no matter what happened. The good reception is the icing on the cake.
"Marty is very sensitive about people and actors. He takes what actors give him and uses it. He is aware and well-informed about things and likes to read stuff. Directors have to be well-rounded in many facets of life. He's really great."
Meanwhile, Robert also has a close bond with his co-star Al Pacino, who recently said the pair have "helped each other" out throughout their lives, after they first became friends in 1968.
He said: "Early on in our careers, we connected from time to time and we found we had similar things happening to us. Our lives took on a whole different kind of thing.
"[Camaraderie] got us together ... We're really close. We don't see each other very much, but when we do, we found we shared certain things. In a way, I think we've helped each other throughout life."