The Cake actress wore a slinky Saint Laurent design complete with sequin halter-neck bodice and thigh-high split.
Backless, cinched in at the waist and teamed with Neil Lane jewellery (not to mention that engagement ring bling), Jennifer's look was all elegance.
Justin Theroux is one lucky guy.
Noir is Jen's shade and she's sticking to it, but she did make one change - the 45-year-old star swapped her signature straight down do for a sleek updo.
While she lost out on the Best Actress in a Motion Picture award to Julianne Moore, Jen was all grace and smiles during the ceremony and at the 2015 InStyle and Warner Bros after party at The Beverly Hilton Hotel.
Other ladies wearing black on the red carpet included Amal Clooney, who wore an asymmetric Dior gown complete with long white gloves (her own) and matching clutch bag. Jane the Virgin's Gina Rodriguez and singer Lorde who played it sharp and sophisticated in a trouser suit.
Just more proof top-to-toe black will never go out of style. And when accessorised right, it's not a bit boring.
LOVE A RED CARPET DRESS? Flick through this gallery to see all of the best looks from this year's Golden Globes.