Selena Gomez and The Weeknd turned the streets of Harlem into their own runway show ... flanked by bodyguards, of course.

The couple stepped out Monday night dressed to the nines -- more so Selena, but Abel was rocking a sweet jacket too -- as they did dinner at famed Italian restaurant RAO's.

No such thing as a low-key dinner for these 2 anymore though -- they had a small army surrounding them at all times.

Gotta say, they've come a long way since their initial PDA in front of cameras -- 'memba that?