Rihanna's attempt to hide her boyfriend is funny ... just look at him laugh his ass off.
RiRi was leaving Chiltern Firehouse, the hottest restaurant in London, Wednesday night ... and gave it the ol' college try to shield bf Hassan Jameel with her moniker.
No dice ... Rihanna's pretty recognizable and it's not hard to match that grin to the one back in June ... when RiRi and Hassan were hanging out.
Not sure what Hassan's laughing about, but it certainly can't be about this.