The Weeknd and Selena Gomez Grammy Party with Rihanna While Justin Throws Shade

The Weeknd and Selena Gomez didn't let a little thing like ZERO Grammy Awards stop 'em from hitting the post Grammy party scene.

The couple hooked up to hit Rihanna's party at 1 OAK on the Sunset Strip. He performed during the award show, one of the night's highlights, but it appears his gf was a no-show. Selena wasn't nominated, and neither was The Weeknd -- "Starboy" was released after the cutoff date.

His hit record did get a shout-out Sunday night, with a heaping side of SHADE, from Justin Bieber.

As we told you ... Justin bailed on the Grammys this year, but during the ceremony he went live on Instagram and took a shot at his ex-gf and her new man.

Ice cold.