Sienna Miller was supported by her family on Sunday night, as she was joined by her boyfriend and daughter at the premiere of her film Horizon: An American Saga premiere during Cannes Film Festival.

The actress, 42, put on an ethereal display in a semi-sheer gown as she arrived on the red carpet with boyfriend Oli Green, 27, and lookalike daughter Marlowe, 11.

It marks Marlowe's first ever red carpet appearance, with her famous mother only showing her face for the first time in July 2020 in a spread for Vogue.

Sienna shares Marlowe with her ex Tom Sturridge, who she was in a relationship with from 2011 until 2015.

While the movie star only just recently welcomed a second daughter and first child with Oli, in January. 

Sienna Miller was supported by her family on Sunday night, as she was joined by her boyfriend and daughter at the premiere of her film Horizon: An American Saga premiere during Cannes Film Festival 

The actress, 42, put on an ethereal display in a semi-sheer gown as she arrived on the red carpet with boyfriend Oli Green, 27, and lookalike daughter Marlowe, 11

It marks Marlowe's first ever red carpet appearance, with her famous mother only showing her face for the first time in July 2020 in a spread for Vogue

Sienna held hands with her oldest child as Marlowe and Oli supported her at the premiere of her new epic Western film.

The Anatomy of a Scandal star commanded attention in a flowing lavender gown with layers of ruffles.

The sheer material of the draped dress allowed a glimpse of Sienna's incredible figure in a plunging playsuit underneath.

Adding a touch of sparkle to the ensemble, the Golden Globe nominee sported a diamond necklace.

Sienna added silver strappy heels to give herself an extra few inches and a bright pink lipstick for a pop of colour.

While daughter Marlowe looked the spit of her stunning mother, wearing a sweet pink dress with a large bow.

Beside them Oli looked typically dapper in a black suit, white shirt and navy tie, while sporting brown rimmed sunglasses.

Sienna was soon joined by her co-stars on the red carpet, including the film's co-writer, director, producer and lead star, Kevin Costner.

Sienna shares Marlowe with her ex Tom Sturridge , who she was in a relationship with from 2011 until 2015

 While the movie star only just recently welcomed a second daughter and first child with Oli, in January

 Sienna held hands with her oldest child as Marlowe and Oli supported her at the premiere of her new epic Western film

The Anatomy of a Scandal star commanded attention in a flowing lavender gown with layers of ruffles

The sheer material of the draped dress allowed a glimpse of Sienna's incredible figure in a plunging playsuit underneath

Adding a touch of sparkle to the ensemble, the Golden Globe nominee sported a diamond necklace. Sienna added silver strappy heels to give herself an extra few inches and a bright pink lipstick for a pop of colour

While daughter Marlowe looked the spit of her stunning mother, wearing a sweet pink dress with a large bow

Sienna was soon joined by her co-stars on the red carpet, including the film's co-writer, director, producer and lead star, Kevin Costner

Kevin, 69, looked more handsome than ever in a black three-piece suit, including a waistcoat and matching bowtie

Like Sienna, he made the premiere into a family affair by also bringing along his daughter, youngest child Grace, 13

The Oscar winner is the father of seven children - sharing Annie, Lily and Joe with his ex-wife Cindy Silva, son Liam with ex Bridget Rooney and Cayden, Hayes and Grace with his second ex-wife, Christine Baumgartner

Ella Hunt, Abbey Lee and Jena Malone also made glamorous appearances on the red carpet, all opted for semi-sheer and pastel coloured gowns

Sienna beamed as she greeted Ella, who left little to the imagination in her flowing one-shouldered gown

The actress, 26, who plays Juliette Chesney in the film, dared to bare all in the completely sheer gown

Kevin, 69, looked more handsome than ever in a black three-piece suit, including a waistcoat and matching bowtie.

Like Sienna, he made the premiere into a family affair by also bringing along his daughter, youngest child Grace, 13.

The Oscar winner is the father of seven children - sharing Annie, Lily and Joe with his ex-wife Cindy Silva, son Liam with ex Bridget Rooney and Cayden, Hayes and Grace with his second ex-wife, Christine Baumgartner.

Horizon stars Ella Hunt, Abbey Lee and Jena Malone also made glamorous appearances on the red carpet, all opted for semi-sheer and pastel coloured gowns.

Sienna beamed as she greeted Ella, who left little to the imagination in her flowing one-shouldered gown.

The actress, 26, who plays Juliette Chesney in the film, dared to bare all in the completely sheer gown.

Abbey looked statuesque in a halterneck purple dress, which was encrusted in gems and also see-through, showing off her long legs and bodysuit underneath.

While Jena, who plays Ellen/Lucy, looked regal in an angelic white gown with a high-neck and flowing cape over her shoulders.

Abbey looked statuesque in a halterneck purple dress, which was encrusted in gems and also see-through, showing off her long legs and bodysuit underneath

While Jena, who plays Ellen/Lucy, looked regal in an angelic white gown with a high-neck and flowing cape over her shoulders

Isabelle Fuhrman (far right), who stars as Diamond Kittredge in the film, stood out from the crowd in a strapless red dress

Her show-stopping gown boasted a full layered skirt and was adorned with sparkling three-dimensional roses

 And Luke Wilson (far right), who stars as Matthew Van Weyden, cut dapper figure in a black suit and navy silk tie, with casual brown trainers

Wasé Chief, who takes on the role of Liluye (far right), showcased her incredible figure in a skintight white dress, with feather detailing

Isabelle Fuhrman, who stars as Diamond Kittredge in the film, stood out from the crowd in a strapless red dress.

Her show-stopping gown boasted a full layered skirt and was adorned with sparkling three-dimensional roses. 

Georgia MacPhail opted for a vintage style outfit, wearing a black 1950s polka dot dress with a yellow belt.

Wasé Chief, who takes on the role of Liluye, showcased her incredible figure in a skintight white dress, with feather detailing.

And Luke Wilson, who stars as Matthew Van Weyden, cut dapper figure in a black suit and navy silk tie, with casual brown trainers.

As well as her family, Sienna was also supported by her friend and ex-boyfriend's new girlfriend, Alexa Chung.

The presenter, 40, is currently dating Sienna's ex and Marlowe's father Tom, 38, but has formed a close bond with Sienna.

Alexa and Tom have been spotted hanging out with Sienna and Oli frequently and Sienna previously gushed that their family dynamic was 'genuinely very loving and cosy and great. It's ideal. It's incredible. We are very lucky.'

As well as her family, Sienna was also supported by her friend and ex-boyfriend's new girlfriend, Alexa Chung

The presenter, 40, is currently dating Sienna's ex and Marlowe's father Tom, 38, but has formed a close bond with Sienna

Alexa and Tom have been spotted hanging out with Sienna and Oli frequently and Sienna previously gushed that their family dynamic was 'genuinely very loving and cosy and great. It's ideal. It's incredible. We are very lucky' 

Alexa turned up the heat on the red carpet in a racy black gown, with a plunging neckline that showed off her cleavage

Adding her signature edgy style, the model sported a chunky bangle, strappy high heels and oversized sunglasses

Also in attendance at the star-studded premiere was Julianne Moore, who ensured all eyes were on her in an off-the-shoulder emerald number

The actress, 63, looked the epitome of chic in the fitted green dress which featured an eye-catching ruffled neck detail

While she added a chunky gold necklace and some pointed gold heels for the finishing touches

Julianne showcased her age-defying looks by pulling her signature red hair back into a classy bun and adding flawless face of makeup

While Michelle Yeoh put on daring display in a strapless leather gown, that showcased her svelte figure

Her racy dress boasted a corseted burgundy bodice and a cream and red skirt, made up of layered leather strips

The Oscar winning actress, 61, added a cream clutch, nude high heels and dazzling diamond and pearl necklace

Alexa turned up the heat on the red carpet in a racy black gown, with a plunging neckline that showed off her cleavage. 

Adding her signature edgy style, the model sported a chunky bangle, strappy high heels and oversized sunglasses.

Also in attendance at the star-studded premiere was Julianne Moore, who ensured all eyes were on her in an off-the-shoulder emerald number.

The actress, 63, looked the epitome of chic in the fitted green dress which featured an eye-catching ruffled neck detail. 

While she added a chunky gold necklace and some pointed gold heels for the finishing touches.

Julianne showcased her age-defying looks by pulling her signature red hair back into a classy bun and adding flawless face of makeup.

While Michelle Yeoh put on daring display in a strapless leather gown, that showcased her svelte figure.

Her racy dress boasted a corseted burgundy bodice and a cream and red skirt, made up of layered leather strips.

Candice Swanepoel displayed her model credentials as she arrived in a fitted black satin gown, which clung to her slender frame

The voluminous off-the-shoulder neckline ensured a glimpse of skin, while also staying elegant

The model elevated the look with a diamond pendant necklace and matching earrings, while slicking her hair back in a sophisticated bun

Camille Rowe also opted for a black gown for the premiere, sporting a long-sleeved and high-necked velvet number

Her outfit boasted a dramatic cape detailing that flowed to the floor, while the model opted for no accessories to let her outfit do the talking

The Oscar winning actress, 61, added a cream clutch, nude high heels and dazzling diamond and pearl necklace. 

Candice Swanepoel displayed her model credentials as she arrived in a fitted black satin gown, which clung to her slender frame.

The voluminous off-the-shoulder neckline ensured a glimpse of skin, while also staying elegant.

The model elevated the look with a diamond pendant necklace and matching earrings, while slicking her hair back in a sophisticated bun. 

Camille Rowe also opted for a black gown for the premiere, sporting a long-sleeved and high-necked velvet number.

Her outfit boasted a dramatic cape detailing that flowed to the floor, while the model opted for no accessories to let her outfit do the talking.

Josephine Skriver made sure to display her sensational curves in a figure-hugging white gown.

The sultry number was embroidered with intricate beading and pearls, while boasting a thigh-high slit and backless design.

Josephine Skriver made sure to display her sensational curves in a figure-hugging white gown

The sultry number was embroidered with intricate beading and pearls, while boasting a thigh-high slit and backless design

The Danish model posed up a storm for the cameras, while adding sparkly spiked earrings and matching heels

Ellen Von Unwerth chose a very different look, taking a walk on the wild side with a gold animal print blazer

She completed her androgynous ensemble with a white shirt, black trousers and a bow tie, with strappy heels and a matching handbag

Amy Jackson pulled out all the stops in a revealing black gown with huge off-the-shoulder sleeves

The eye-catching dress also featured racy cutouts across the chest, allowing a glimpse of her cleavage

The Bollywood actress added a yellow diamond choker and matching earrings, with heavy smoky eyeshadow

The Danish model posed up a storm for the cameras, while adding sparkly spiked earrings and matching heels. 

Ellen Von Unwerth chose a very different look, taking a walk on the wild side with a gold animal print blazer.

She completed her androgynous ensemble with a white shirt, black trousers and a bow tie, with strappy heels and a matching handbag.

Amy Jackson pulled out all the stops in a revealing black gown with huge off-the-shoulder sleeves.

The eye-catching dress also featured racy cutouts across the chest, allowing a glimpse of her cleavage.

The Bollywood actress added a yellow diamond choker and matching earrings, with heavy smoky eyeshadow. 

Horizon: An American Saga chronicles a multi-faceted, 15-year span of pre-and post-Civil War expansion and settlement of the American West. 

Kevin plays pioneer Hayes Ellison in the new film, who treks the West through dangerous territory in hopes of a new life.

Horizon: An American Saga chronicles a multi-faceted, 15-year span of pre-and post-Civil War expansion and settlement of the American West 

Kevin plays pioneer Hayes Ellison in the new film, who treks the West through dangerous territory in hopes of a new life, while Sienna stars as Frances Kittredge (pictured)

While Sienna stars as Frances Kittredge in the period epic, which is set to be released in two chapters on June 28 and August 16 this year.

They mark the first two of four planned film instalments for the movie series, which Kevin has been desperately trying to bring to life for more than 30 years now/

The Dancing With Wolves star is thought to have personally raised up to $50 million of Horizon's $100 million budget.

Speaking during a press conference at the Carlton hotel earlier on Sunday, he and Sienna gushed about their deep regard for each other.

Sienna admitted that she would go 'to the ends of the earth' for Kevin, and called him 'phenomenal'.

While Kevin said of her: 'I think she's one of our great actresses. Her outward beauty is undeniable, but she's so skilled as an actress.' 

Sienna said: 'I grew up watching Westerns. I think my idea of cinema was a Western when I was a little girl, and then Dances With Wolves was a huge, huge part of my life.

'I had two rabbits called Two Socks and Cisco,' referring to the wolf and horse in the film. 'I got this call that Kevin wanted to talk to me, and then I got sent four scripts and I thought it must be a series. 

Speaking during a press conference at the Carlton hotel earlier on Sunday, Kevin and Sienna gushed about their deep regard for each other

Sienna admitted that she would go 'to the ends of the earth' for Kevin, and called him 'phenomenal'

While Kevin said of her: 'I think she's one of our great actresses. Her outward beauty is undeniable, but she's so skilled as an actress'

Sienna said: 'I grew up watching Westerns. I think my idea of cinema was a Western when I was a little girl, and then Dances With Wolves was a huge, huge part of my life'

'There are four of them, but they're so big, so it didn't really make sense. And then we had this great conversation. I'd really go to the ends of the earth for him, I think he's phenomenal.'

Kevin said that the stories of the women are central to the film, saying: 'It's almost impossible to imagine a West without women, isn't it? The West doesn't carry on without women.

'And they understand that they were basically trying to keep their families clean and fed, and women were worked to death. 

'And if they lost their man, there's every opportunity that their life could become something unimaginable, bad. 

'That's why Sienna's character moves so quickly to bring a man into her life, because she knows how vulnerable she could be, and she doesn't care about her reputation to do it. And we would taboo that now: That's too quick, she's moved too quick.'

He added: 'I am not looking for kudos because women are in it. For me, they're not in it, they actually dominate the movie, to be honest. Every one of those women dominate when they're on the screen.'

Kevin said that the stories of the women are central to the film, saying: 'It's almost impossible to imagine a West without women, isn't it? The West doesn't carry on without women' (Sienna pictured in the film)