Well, this is a big change!

Sienna Miller showed off her new red locks last night at the launch of her older sister, Savannah Miller's, fashion label. 

The actress took time out of her Hollywood schedule and snuggled up with her sister as they celebrated the launch of Nine by Savannah Miller for Debenhams.

The event took place in the swanky Roof Terrace at the Ham Yard Hotel in London. 

While the fashion designer was dressed in a glamorous silver mini dress, Sienna, 33, kept things simple to show off her new do'. 

She wore a grey loose jumper, black skinny jeans and suede peep-toe shoes, while keeping her make up natural. 

Sienna is currently busy filming her new movie, The Lost City of Z, which she's been shooting in Northern Ireland. 

The actress is playing to role of Nina in the period movie, based on David Grann's 2009 novel about the British explorer Percy Fawcett. 

The movie is shaping up to be one of the most star-studded productions of 2016, with Brad Pitt and Robert Pattinson also invloved.