Enrique Iglesias & Anna Kournikova -- How'd They Make it Last??? (VIDEO)

Enrique Iglesias and Anna Kournikova went out Friday night. Lots of photogs took pics and shot video. They didn't say anything. But he put his arm around her and they're together ... after 15 years.

Enrique and Anna hit up Palm Restaurant in Bev Hills. He's 41, she's 35. She was 20 when they hooked up and he was 26. They're both superstars, with lots of options. They have no kids holding them together.