They might star as Girls, but the actresses of the hit HBO series were nothing short of ladies while walking the red carpet at their season four premiere on Monday.

Zosia Mamet, Lena Dunham, Allison Williams and Jemima Kirke all looked sophisticated and chic at the event held at the iconic American Museum of Natural History in New York City.

The stars of HBO's Girls pose together on the red carpet in New York City

Lena, 28, showed off a new sleek brown bob (a departure from her recent platinum blond look) and as usual, opted for a more fashion-forward wardrobe choice — a sequin-detailed Creatures of the Wind dress paired with Irene Neuwirth earrings.

Fashion darling Allison, 26, stuck to her feminine and sophisticated style with a regal blue and black Monique Lhuillier strapless gown. She paired the fancy dress with ladylike black heels and her hair pulled back in an almost royal manner.

Zosia, on the other hand, kept it fun in one hue: the 26-year-old, who plays fast-talking Shoshanna, wore a bright red leather Alexander McQueen mini with matching heels and lip color.

Jemima, 29, honored her free-spirited Girls character with a flowy satin black dress by Sophia Webster that showed just enough leg — and tattoo.

Andrew Rannells strikes a pose with a fan

The girls had more reason than one to celebrate — HBO picked up the show for a season five

Several noted celebrities including Kathy Griffin and Andrew Rannells were on hand for the party, but it seems Lena was most excited to share the night with one special woman— her mom:

Girls returns with season four on January 11.

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