And Thursday evening was her big night when she finally walked the red carpet in Leicester Square for the premiere of movie, Diana.
While she may have flashed a bit more flesh than the late Princess Of Wales would have opted for herself, she would have still no doubt have approved of Naomi's stunning choice of outfit.
Leading lady: Naomi Watts steals the show at Thursday night's Diana premiere in Leicester Square in a white gown with large side split
The actress, 44, wowed in a figure hugging white frock with a large side split up one side and a cross-over cut exposing her chest.
She showed off her impressive physique in the ensemble which emphasised her petite frame.
Naomi even gave a hint of her toned legs as well as she put her left leg on display through the split and wore a pair of black high heels.
She's got style: Naomi knew all eyes would be on her for the coveted role so made sure she stunned for the evening
Toned: Naomi looked confident as she paraded around for the cameras on Thursday evening
The wait is over! It has been one of the most highly anticipated movies of the year and is finally set for release on 20 September
The star wore large earrings and a simple bracelet around her right wrist, but she kept her hair 'do simple.
Watts opted for an up 'do for the occasion with her long fringe hanging loose.
Naomi revealed at the premiere that she wanted to play Princess Diana because she was such a "complex" woman.
Stunner: Naomi walked the red carpet outside the Odeon in Leicester Square along with her castmatesThe 44-year-old actress portrays the late royal in new movie Diana - which is based on the book Diana: Her Last Love and focuses on the last two years of her life including her romance with Dr. Hasnat Khan.
Naomi initially turned down the part twice but was compelled to take on the role because she found Diana - the mother of British Princes William and Harry - so fascinating.
Speaking at the world premiere of the film at the Odeon cinema in London's Leicester Square tonight, she said: 'Any woman I take on (on screen) I want them to be all things.
Crowd pleaser: Before she headed inside for the screening she ensured she greeted the waiting fans and signed autographs
Photo opp: Naomi posed up next to her movie co-star Juliet Stevenson, who wore a floorlength silver lace gown
Camera ready: Naomi made sure all camera angles were covered as she twirled around in her dress
'Someone who is going through something, some kind of transformation and this story is definitely that.'
Naomi did a lot of research on Diana - the ex-wife of Prince Charles who tragically died in a Paris car crash in 1997 - and found her to be a very funny and mischievous person.
Reunited: Naomi cuddled up to Naveen Andrews, who plays Dr. Hasnat Khan in the film, the doctor she once dubbed Mr Wonderful
Centre stage: Naomi got camera ready as she posed in her stunning white dress
Her big night: Watts has previously admitted she's nervous about how the film and her portrayal will be perceived
All together now: Naomi Watts and Naveen Andrews were joined by Stephen Jeffreys (writer), Juliet Stevenson, Daniel Pirrie and director Oliver Hirschbiegel
All white: Naomi greeted guests before finally making her way to her seat to watch the film and the all important reactions
She added to BANG Showbiz: 'It seemed to me, in the research that I did, that Diana had a great spirit and a great sense of humour and a mischievous way and I definitely wanted to incorporate that in my portrayal.'
Naomi was joined on the red carpet by Naveen Andrews - who plays her on screen lover Dr. Khan - the film's director Oliver Hirschbiegel, Douglas Hodge, who portrays Diana's butler Paul Burrell, and star guests including Andy Serkis.
The British-born actress - who moved to Australia at the age of 14 - also recently spoke out about how nervous she feels about the upcoming release of Diana.
'I might go into hiding,' Naomi told Instyle magazine. 'More than twice I thought about not doing this.'
The talented star even added that she 'might have to leave the country' if the film doesn't get a good reaction.
Diana - a biopic that traces the life of Princess Diana of Wales - is scheduled for release on September 20 in the UK and November 1 in the USA.
She also recently revealed that during that process she fell 'in love' with the late Princess of Wales.
Actress Laura Dern has interviewed Naomi for a feature on the star in Hamptons Magazine, and Naomi reveals how she admired Diana's quest to survive some of her most testing times.
'I can't really think of many people who can survive that level of fame,' Naomi told Laura.
Proud: The pair looked happy to finally be showing off their hard work at the screening
Interacting: She made her way down the row of waiting fans taking her time to chat to them
Taking her time: She accessorised with some large earrings and her blonde locks in a simple up 'do
Star status: The movie will be seen on cinema screens later this month in the UK and from November in the US
'It's horrible to imagine that life. But she kept trying to get better - that's why I fell in love with her.'
'She was doing so much work to survive that, and fighting to be happy. Already she was going to have a tough time because of being separated from her mother for such a long time, then getting thrust into the royal lifestyle at 19, and being pushed out of it with the breakdown of her marriage.'
At Thursday night's premiere she was also joined by her co-star Naveen Andrews, who plays Dr. Hasnat Khan, the last man she ever loved.
Focusing on the public pressure and media spotlight affecting their romance, a trailer that was released last month proves to be a harrowing insight into the movie's focus on the private life of the former Princess of Wales.
The production have done well to recreate classic images of Diana throughout the film, focusing on the last two years of her life as she continued her charity work, supporting AIDS victims and campaigning against landmines with the Red Cross.
But it was her little known relationship with a heart surgeon that grips our attention as the truth behind their failed union comes out in the trailer.
At first, Diana's attraction to Khan stems from his treatment of her as a normal person, with her saying to a friend: 'He doesn't treat me like a princess, it's almost like he doesn't know who I am.'
And while the trailer shows a montage of clips of the two enjoying the early stages of their romance, it seems the media attention surrounding the princess was far too much for Hasnat to handle.
ON the night Naveen was reunited with Watts once more and cuddled up to photos with her as he showed of his dapper style in a suit.