Millie Bobby Brown is on a high-fashion hot streak ... showing off her sultry side in a sheer underwear-revealing black lace gown, complete with a faux fur neckline and cuffs.

XNY/Star Max//Getty Images Brown was striking in a black floral lace maxi dress with a dramatic ... proving his status as a fashion insider. Up top, he wore a workwear-inspired dark denim jacket ...

Millie Bobby Brown is officially in her fashion girl era ... out in New York City on March 11 wearing a fully sheer, black lace maxidress. The dress was so sheer, that Brown's matching black ...