EXCLUSIVE

Harvey Weinstein was attacked Tuesday night at a restaurant ... TMZ has learned.

Weinstein was at Elements restaurant at the Sanctuary Camelback Mountain Resort in Scottsdale, eating dinner with his sober coach when 2 men sat at a table next to them.

One of the men -- Steve -- tells TMZ he walked up to Weinstein and told him he loved his movies and would like to take a photo with him. Steve says Weinstein became belligerent and told him to buzz off. The manager of the restaurant says Weinstein was not belligerent -- she says to the contrary he was "very sweet about it" and said, "I'd rather not take a picture right now." The manager says the two shook hands and Steve went back to his table.

At around 9 PM, Weinstein and his sober coach got up to leave at the same time Steve and his dinner companion were leaving. Steve tells TMZ he had "quite a bit to drink," told his friend to fire up his cell phone and shoot video of what was about to happen.

Steve says he walked up to Weinstein and said, "You're such a piece of s*** for what you did to these women," and then punched him in the face twice. He says Weinstein stumbled backward and almost fell.

A restaurant manager says neither attempted punch connected, and the guy was drunk and out of control.