Tom Cruise is beside himself after the death of "Top Gun" director Tony Scott -- claiming, Scott "was a creative visionary whose mark on film is immeasurable."

Tom -- who starred in "Top Gun" back in 1986 -- added, "Tony was my dear friend and I will really miss him ... My deepest sorrow and thoughts are with his family at this time."

As we reported, Scott -- who directed countless major Hollywood films -- jumped to his death yesterday from an L.A. bridge, leaving behind several suicide notes for friends and family.

Scott reportedly suffered from inoperable brain cancer before his death.