The 61-year-old actress posed topless while floating in a swimming pool for the cover of May's Sex Issue of "Vogue Portugal" ... and appears in a series of racy shots inside the mag too.

The provocative set includes Sharon in fishnets and stiletto heels -- legs spread wide open -- staring defiantly at the camera. The pose pays homage to her iconic 'Basic' scene in which she uncrosses her legs during a police interrogation to reveal she isn't wearing underwear.

There's also a shot of Stone completely topless on a couch -- legs crossed this time -- and another features her in a white dress showing off her legs ... another nod to her "Basic Instinct" attire.

In her 'Vogue' interview, Sharon addresses the idea of being sexy in Hollywood, and insists she's not a sex symbol despite her image and film history. She says she worked hard and used her brain to appear "f***able," though.

Yep, still got it.

And, in case you're unfamiliar with her iconic movie scene ... here you go.