Johansson, who won the best actress Bafta for 'Lost in Translation' in 2003 and was nominated for a Golden Globe for Best Supporting actress for her role in Woody Allen's 'Match Point', has been snapped up to be the face of the cosmetics giant's new colour line, High Intensity Pigments.
The 21-year old star, known for her trademark blonde locks and Marilyn Monroe-esque appearance, will feature in TV ads trying out a variety of different hair colours.
According to US fashion paper Woman's Wear Daily, L'Oreal is hoping to generate $50m of sales in the first year with Johansson fronting the hair colour brand.
Johansson said: "It's wonderful to be working with L'Oreal, a company that has celebrated independent women for years."
The actress joins the ranks of A-list celebrities who have appeared in L'Oreal TV ads including 'Desperate Housewives' beauty Eva Longoria, singer Beyonce Knowles and 'Friends' star Jennifer Aniston.
The news comes a week after Johansson was left red-faced on the red carpet at the Golden Globes after an E! Entertainment channel guest reporter touched her breast.
Gay designer Isaak Mizrahi asked Johansson what she was wearing under her red dress. When she joked "not much," Mizrahi grabbed his chance -- and a large handful of her breast.
"It's built in, I just wanna feel it -- oh, I just love that," he said.
When Johansson asked what he was doing, he replied "I'm just taking notes", to which she replied "Well, take all the notes you want".
Johansson made her name as a child star opposite Robert Redford in the 1998 film 'The Horse Whisperer' aged 14.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum.