Duchess of Cambridge Kate Middleton STUNS in floor-length lace gown for 2017 Portrait Gala

The Duchess stunned onlookers with her floor-length look. 

Kate donned a dark green Temperley dress with a lace overlay and sheer long sleeves. 

A dark green ribbon tied in at her waist, with the embroidery covering her décolletage. 

The Duchess of Cambridge wore her brunette hair down for the occasion, with big billowing curls falling around her face.

She matched the show-stopping dress with a metallic gold clutch and gold open toe heels. 

Kate is attending the 2017 Portrait Gala to view the newest exhibitions, greet guests and dine in the London art gallery. 

The Duchess has been a patron of the National Portrait Gallery since 2012. 

Kate will tonight view two exhibitions: the Howard Hodgkin: Absent Friends, and Gillian Wearing and Claude Cahun: Behind The Mask, Another Mask.

It’s the second gala Kate has attended, after she appeared at the first in 2014. 

Earlier this month the Duchess wowed the crowds with her outfit choice at the British Embassy dinner. 

Kate opted for a floor-length ice blue gown by Jenny Packham. 

The silk dress featured a mesh top and a floral design, which she teamed with a diamond bracelet, an equally glistening clutch bag, diamond earrings and silver stilettos.