Winter Olympics -- HEINEKEN ARRIVES IN SOCHI ... Hey Bud, We're Not Afraid!

Heineken ain't afraid of no terrorism -- unlike Budweiser -- TMZ Sports has learned, the Dutch beer company has REFUSED to cancel its Olympics party in Sochi ... after its American cousin pulled out.

A rep for Heineken tells us, the beer titan's party house in Sochi officially opened for business today ... and it's already turnt up big time.

It's a big move ... considering Budweiser shut down all plans to have a presence in Sochi because the company is afraid of the looming threat of terrorism.

But Heineken says Bud's fears are unsubstantiated ... with one rep telling us, "Sochi is actually OK safety-wise."