Her signature style has been copied the world over, see Sienna's hottest hair and beauty looks here.
Over the last four years Sienna Miller has gone from boho beauty to super-sleek siren and the world has watched her every step of the way. One of the biggest style influences around and a constant threat to Kate Moss's style crown, check out our favourite Sienna highlights here.
Fresh as a daisy
A fresh-faced Sienna graced the red carpet for the premiere of Cold Mountain back in 2003, in her supporting role as Jude Law's lady. A newbie in the media spotlight, at just 21 Sienna was already influencing style pages with her boho look. Here she lets her natural beauty shine through with a simple, bare-faced look, opting for rose pink lips, subtle peach cheeks and a soft up-do. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Boho beauty
At the peak of her boho boom Sienna had women everywhere racing for their gypsy skirts and wide-buckle belts. She continued her stella style apace, always one step ahead of her ever-increasing following. Here she keeps her wavy locks looking soft and effortless with a middle-parting fringe that few others could pull off. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Boho beauty
At the peak of her boho boom Sienna had women everywhere racing for their gypsy skirts and wide-buckle belts. She continued her stella style apace, always one step ahead of her ever-increasing following. Here she keeps her wavy locks looking soft and effortless with a middle-parting fringe that few others could pull off. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Prim princess
Two years later and Sienna has successfully shaken off her gypsy skirt glamour and instead embraced a more Sixties mod look with her black pea coat and wide Alice band. Her make-up remains fresh with lashings of black mascara highlighting her blue eyes and bronzed cheeks giving her a sun-kissed glow. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Shaggy chic
We all know that turbulent love lives can produce reactionary haircuts and here's a classic case. A year earlier Jude had publicly apologised to Sienna for his misdemeanour with his nanny and although the pair tried to rekindle their romance, clearly things were never the same. Sienna's response to his philandering ways? To go for 'the chop'. By no means a style that everyone could pull off, Sienna does so with aplomb. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Glamourpuss
Here's proof that by 2006 Sienna had clearly made her mark on the fashion scene, appearing at the Costume Institute Gala in New York. She hit the headlines in a Burberry Prorsum gold-sequinned mini dress that was ripped off everywhere on the high street. Sienna dressed down the look with a messy up-do and plenty of black kohl eyeliner. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Mane madam
Something of a departure for Sienna, she wowed the crowds at the opening night of Madam Butterfly in New York with a perfectly groomed centre parting mane. With paired-down simple make-up, heavily kohled eyes and a touch of silver sparkle on the lower rim, Sienna let her stunning Marchesa gown do the talking. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Heidi heights
This was a love it or hate it moment for Sienna as she posed for the cameras at the 2007 Golden Globe Awards. The homage to Heidi was one of the most-talked about looks on the red carpet that year. As ever, Sienna kept her make-up understated with peachy cheeks and nude lips, all in favour of the wrap around plait that adorned her head. Some said pretty perfect, others a Heidi horror. You decide. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Smoky-eyed siren
When Sienna took on the role of Eddie Sedgewick in Factory Girl, it seemed she had temporarily metamorphosed into the society It girl herself. Here she nods to the Sixties icon at the Santa Barbara Film Festival for the movie premiere, with dark, smoky eyes and freshly highlighted blonde looks. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Honey bee
Six months on and Sienna has ditched the super-blonde tresses in favour of a honey-coloured wavy bob. The shade and cut take years off the actress and the natural wave, teamed with sun-kissed skin gives Sienna that just stepped off the beach and onto the red carpet feel. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html
Vampy vixen
Sienna raised a few eyebrows at the Orange British Academy Film Awards this year, arriving in a sweeping black gown, sleek locks and a slick of berry red lipstick. In a complete departure from the girly, sun-kissed and understated signature look we're used to, Sienna's grown up guise announced to the world that she has grown up and means business. http://www.marieclaire.co.uk/celebrity/a-z/158482/sienna-miller.html