Billy Crystal -- who starred in one of Nora Ephron's greatest films "When Harry Met Sally" -- is crushed by her death ... saying, "I am very sad to learn of Nora's passing. She was a brilliant writer and humorist."
Crystal issued a statement shortly after the Hollywood icon died, adding, "Being her Harry to Meg's Sally will always have a special place in my heart ... I was very lucky to get to say her words."
As we reported, Ephron passed away yesterday following a grave illness. She was 71.