The mom to Prince George, Princess Charlotte and Prince Louis turns 37 on January 9th -- and we're celebrating by taking a look back at her transformation from Prince William's girlfriend to duchess.
There's no doubt that the Duchess of Cambridge is the style icon of our generation. While she often opts for high-fashion British designers such as Alexander McQueen and Jenny Packham, Kate is also known to favor more affordable brands such as Zara and Topshop. And no matter the price tag, she's continued to dazzle with her sartorial choices.
From red carpets to charity events to royal weddings, her style transformation is truly fit for a princess:
Kate Middleton's style transformation
Kate Middleton's style transformation
For the Wimbledon finals, Kate recycled this Jonathan Saunders dress she wore during the Jubilee Royal Tour in 2012.
Kate, William and Harry kicked off the Tour de France in July. Kate was wearing her green Erdem coat and favorite L.K. Bennett sledge pumps.
The Duchess of Cambridge visits an M-PACT Plus Counselling programme at Blessed Sacrament School on July 1st in a coral GOAT dress with cream clutch.
Kate is seen wearing Alexander McQueen to a military event in London.
Duchess Kate attends Order of the Garter in a lovely pale blue Christopher Kane coat.
Prince George of Cambridge walks holding his Catherine, Duchess of Cambridge's hand as they watch Prince William, Duke of Cambridge & Prince Harry play in the Jerudong Trophy charity polo match. Kate is seen wearing a casual striped top and a pair of skinny jeans, while George is wearing an adorable pair of overalls.
The Duchess of Cambridge during an official visit to National Maritime Museum on June 10, 2014 in London, England.
Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge attend a service during the D-Day 70 Commemorations on June 6, 2014.
Catherine, Duchess of Cambridge holds Prince George of Cambridge as they leave Fairbairne Airbase to head back to the UK after finishing their Royal Visit to Australia.
Catherine, Duchess of Cambridge attends a reception hosted by the Governor General Peter Cosgrove at Government House on April 24, 2014 in Canberra, Australia.
Kate attended the SportsBall, donning a laser-cut, black lace Temperley London cocktail dress, paired with her Jimmy Choo heels and Alexander McQueen clutch.
Kate looked lovely in London, wearing an Orla Kiely skirt and MaxMara coat as she received flowers from a young girl.
Kate recycled an Orla Kiely dress and her Aquatalia boots for a charity visit with William.
Kate wore a pretty black Temperley coat to honor Remembrance Day in London, wearing her hair in ringlets.
In honor of Poppy Day, William and Kate stepped out in London -- Kate wearing her long scarlet L.K. Bennett coat.
Kate attended a charity gala the following day, wearing an elegant navy Jenny Packham gown.
Kate chose Alexander McQueen for Prince George's Christening.
Kate attended the SportsAid Athlete Workshop just a few months after having Prince George. She wore a pre-pregnancy outfit: her J.Brand skinny jeans, Ralph Lauren striped top, navy Smythe blazer and Stuart Weitzman wedges.
Kate and William attended a gala for the Tusk Trust, Kate glittering in Jenny Packham.
Kate joined William out and about in Anglesey, wearing a Zara top, Paige denim jeans and a Ralph Lauren jacket.
Kate wore another Seraphine knot-front dress for the photo while William was casual in a gingham button down. And in this photo, both the Middletons' family dog and Lupo made the cut!
Kate and William pose with Prince George for the family's first official portraits at her family's home.
Kate definitely had a new mom glow about her when she left the Lindo Wing of St. Mary's Hospital.
When Wills and Kate took off to go visit her parents in Bucklebury for the first few weeks after George's birth, she wore a dress by Seraphine perfect for new moms.
Kate wore a bespoke Jenny Packham blue polka dotted dress when she presented her son to the world, and she looked lovely.
For her last official appearance before giving birth, the Duchess chose pale pink Alexander McQueen at the 2013 Trooping the Colour.
Kate was glowing as she named a cruise ship in a printed Hobbs coat.
Kate looked positively lovely at the Queen's Coronation service in one of her favorite designers, Jenny Packham, a light peach, almost nude lace empire-waisted dress.
Kate was bold and bright at this year's Garden Party, wearing a bespoke version of the Marella coat by Emilia Wickstead.
Kate visited Naomi House on the day of her wedding anniversary, wearing a peach coat by Tara Jarmon.
Kate visited the Harry Potter sets at Warner Bros with William and Harry, wearing in a polka-dot dress by Topshop.
Kate attended an event at the National Portrait Gallery, wearing a '50s-inspired, powder blue Emilia Wickstead dress and grey suede pumps.
Kate visited a primary school in a pretty Erdem floral dress.
Kate attended the National Review of the Queen's Scouts, wearing a mint green Mulberry Coat, Whiteley fascinator and her L.K. Bennett pumps. As you can see, the Duchess finally popped and her baby bump was fully visible.
Kate donned her red Armani coat, as seen on her in 2006, for the visit to Scotland.
During a visit to Scotland, Kate and Wills met well wishers, played some ping pong, field hockey and basketball while she wore this tartan coat by British brand moloh.
Kate visited the Great Tower Scout camp, keeping warm in green rain boots, a green army jacket and a knit crochet hat.
Kate visits the Baker Street Underground Station in this teal Malene Birger coat, and true to royal style: a pretty black fascinator.
Dressed in a pretty white Redgrave Goat collarless coat over a dress from Topshop, Kate visited the headquarters of Child Bereavement UK.
Kate Middleton wore this black Topshop dress as she visited the headquarters of Child Bereavement UK.
The Duchess of Cambridge attended the St Patrick's Day Parade at Mons Barracks in the same gorgeous green Emilia Wickstead coat of the previous year.
Kate attended the fourth and final day of the Cheltenham Festival in a gorgeous peach wool coat by Joseph.
Kate visited Grimsby in a gorgeous brown Hobbs coat, with her baby bump just starting to show.
Kate showed off her baby bump in a patterned MaxMara dress and simple pumps during a visit to Hope House.
Kate looks on in a pretty Whistles dress after viewing her first official portrait.
Kate left the hospital, after being admitted for severe morning sickness, in a navy coat by Diane von Furstenberg.
Kate played hockey in Alexander McQueen while visiting St. Andrews University.
Kate wore this MaxMara Studio coat over a leopard-print dress for her and William's first visit to Cambridge.
Kate was glowing in an emerald green Mulberry dress for an opening at the Natural History Museum.
Kate dons her lace Temperley London gown once more, this time adding a pop of red with her Alexander McQueen clutch.
Kate attended a royal reception for team Great Britain's Olympic and Paralympic athletes, wearing a black floral dress with sheer sleeves.
Kate bends down to receive flowers from an adorable two-year-old, looking lovely in Alexander McQueen.
Back in the UK, Kate and Wills attend the official launch of the new Football Centre, the Duchess wearing a Reiss coat.
Kate wore this navy eyelet Mulberry dress with traditional adornments during their visit, with her hair in natural waves.
Kate prepared to dance with traditional dancers, in a much cooler grass skirt than we've ever seen.
The royal couple boarded a plane, Kate wearing a pale yellow eyelet dress and Stuart Weitzman wedges.
The Duke and Duchess smiled in traditional Island clothing as they visited the Governor General's house.
This yellow Jaeger shirtdress was light, bright and cool for the warm island weather.
On day 6, Kate and Wills arrived at the Solomon Islands, Kate dressed in a bright Jonathan Saunders dress.
The casual duo cross a bridge at a Rainforest Research center in Malaysia.
Kate wore this sparkling Alexander McQueen to a dinner with Malaysia's Head of State.
Kate wore a pale teal dress to visit the Memorial Cemetery in Singapore, looking back thoughtfully as she walked beside her husband.
While in Malaysia, Kate wore an ice blue lace Temperley London dress, with her hair pulled back in a pretty updo.
On Day 4, Kate and William visited a Mosque, respectfully removing their shoes, Kate wore a headscarf and looked lovely in white.
Kate looked gorgeous in a floral Erdem dress during the British Gala reception.
She also wore a lovely Alexander McQueen skirt and jacket with Stuart Weitzman wedges.
On day 2, Kate wore this sheer Raoul dress and nude pumps.
Kate and William kicked off the 2012 Diamond Jubilee tour in Singapore, the Duchess wearing a vibrant dress by Prabal Gurung.
Kate looked chic and professional at the Paralympics Day 4 medal ceremony.
Kate attends the 10th day of the Olympics in a zipped-up windbreaker for the sailing events.
Wills and Kate celebrate a big win for the UK during the Olympics.
The Olympics took London by storm, and the young royals weren't going to miss it. Kate sported UK colors in this striped top and navy jeans.
Kate and William visited Bacon's College with Prince Harry, Kate dressed in a grey and white checked dress.
Our three favorite royals wait to receive the Olympic Torch at Buckingham Palace on it's route around Britain to the Olympic Stadium.
Kate looked vibrant in Stella McCartney while visiting the National Portrait Gallery.
Kate looked chic in white at Wimbledon, carrying a fun animal print clutch.
Kate payed homage to Scotland with her clutch while she watched as Prince William was installed as a Knight of the Thistle in Edinburgh.
Time for the Order of the Garter, and while most members of the royal family were in pale hues, Kate's Alexander McQueen stole the show.
Kate wore wellies to a polo match, with casual jeans and her pooch Lupo by her side.
Kate waved from a carriage during the Trooping the Colour ceremony, wearing one of her favorite designers, Erdem.
The Diamond Jubliee continues, and Kate is seen in a nude lace Alexander McQueen dress with a Jane Taylor fascinator.
Kate wore a vibrant red Alexander McQueen dress, carrying a clutch by the same designer and sporting her favorite L.K. Bennett heels during the Diamond Jubilee celebrations.
Kate is pretty in pink at the Queen's Garden Party at Buckingham Palace, wearing an Emilia Wickstead dress and classic nude heels.
Ok, so maybe this photo is more about the puppy-love than the dress, but the Duchess still looks chic, even while playing with her and Wills' pup, Lupo!
Attending an Olympic Concert, Kate dominated the red carpet in a lace-back Jenny Packham gown.
Kate shows a little leg in this sleek Roland Mouret gown.
In one of our favorite looks, Kate had the embellishment on the neckline of this Matthew Williamson dress added just for her -- and she looked gorgeous.
The Duchess is a hard worker! Helping to plant a tree, Kate still looked totally glam in a vibrant blue Reiss dress.
It was St. Patrick's Day, and Kate looked gorgeous in green, a belted Emilia Wickstead dress.
Kate looked cute and casual in coral skinny jeans while playing hockey with the Olympic team.
Kate wore an Orla Kiely dress for a visit in South London.
Kate wore this peplum skirt suit by L.K. Bennett and a James Lock hat during a visit to Leicester, England.
Kate wore this slightly distressed tweed Missoni coat to tea with the Queen and Camilla.
Kate visited schools in Oxford, wearing a flared, bird-print Orla Kiely dress.
Kate wore this brown Hobbs coat to visit Liverpool, pairing it with black stockings and pumps.
Kate visited the National Portrait Gallery in a belted grey jacket with a wide collar.
Attending the premiere of War Horse in the UK, Kate wore a lace Temperley London gown.
The royal family attended a Christmas Day service, all in chic jackets and boots as they arrived together.
Just before the holidays, the Duke and Duchess visited a homeless charity, Kate in a simple Ralph Lauren turtleneck dress.
Prince William, Kate and Prince Harry arrive at the Imperial War Museum, all dressed in their black-tie best.
Kate spoke with dinner guests at a reception at St. James Palace, wearing a silver one-shouldered gown.
A beautiful duo: Kate wore this crimson Beulah London gown, adding some vibrance to Fall in London.
Kate looked lovely in Amanda Wakeley as she and William visited the Royal Marsden Hospital.
The Duke and Duchess visited Birmingham, Kate wearing Alexander McQueen.
Kate sparkled in this classic drape dress by Roksanda Ilincic.
Kate and Wills are back in the U.K., the Duchess wearing a beige v-neck dress for the opening of the state rooms in Buckingham Palace.
Kate in Santa Barbara, in a floral Jenny Packham dress.
Kate and Wills attended the BAFTA Awards, Kate showing off a tiny waist in this Sarah Burton for Alexander McQueen floor length gown.
Kate wore this grey shift by London-based designer Roksanda Ilincic while in Los Angeles.
The Duke and Duchess arrived in Los Angeles, Kate in a bright green dress by one of our favorite designers, Diane von Furstenberg.
Kate looked lovely in this canary yellow Jenny Packham dress, but battled with the wind at Calgary International Airport.
The Duke and Duchess boarded a Canadian Airforce jet, Kate wearing J. Brand skinny jeans and L.K. Bennett slingback wedges.
Kate looked cool and casual in boat shoes and jeans.
Kate and Wills smile at one another, the Duchess dressed in Sarah Burton for Alexander McQueen on their 5th day in Canada.
The newyweds are cute and casual, in a rare embrace (public, at least!) after taking part in a dragon boat race.
Kate wore this simple white shift during their Canada visit, carrying her favorite L.K. Bennett "Natalie" clutch.
On day 4 of their Canada visit, Kate was seen in a brilliant blue Erdem dress with lace detailing on the bodice.
Kate wore this grey shift dress while in Canada, with a pointed collar and cuffed sleeves.
Kate was a bronzed beauty in this long-sleeved, purple Issa dress on the royal couple's Canada tour.
Kate looks over her shoulder as she and Wills attend Canada Day celebrations in Ottowa. She was wearing a white Reiss dress with bold red accents in her fascinator and heels.
Kate wore a lace Erdem shift dress and nude L.K. Bennett heels while attending the wreath-laying ceremony at the National War Memorial in Canada.
Kate wore this bold Alexander McQueen military-style coat while visiting army Barracks in Windsor.
Kate and Camilla, Duchess of Cornwall, wearing pretty coats to the Order of the Garter Service.
Kate wore her Jane Troughton cornflower blue brocade coat to the church service celebrating the 90th birthday of Prince Philip.
Kate and William were the picture of elegance at the 2011 Trooping the Colour ceremony for the Queen's birthday.
Kate and her sister Pippa attend a friend's wedding, both dressed in black and white patterned dresses and matching court shoes.
Kate attended the 10th Annual ARK Gala Dinner in a stunning floor-length embellished Jenny Packham gown.
Kate attended Derby Day, everyone dressed to the nines. The Duchess was in a white Reiss dress and beige fascinator.
The Duchess met Michelle Obama in Buckingham Palace, wearing a cap-sleeved neutral Reiss dress.
Kate and William headed out for their honeymoon the day after their wedding, Kate dressed in a simple belted blue dress and her L.K. Bennett wedges.
Kate leaving Clarence House to attend the evening celebrations following her wedding to Prince William, in a pretty satin dress with an embellished belt showing off her tiny waist.
The new Duke and Duchess of Cambridge kiss on the balcony of Buckingham Palace to cheers from the crowd.
The blushing bride steps out of Westminster Abbey, stunning in her Sarah Burton for Alexander McQueen gown.
Here comes the almost-bride... Kate smiled for the camera as she arrived at the Goring Hotel with her mom and sister the day before her wedding. She looked stunning in a patterned Issa dress and L.K. Bennett wedges.
Kate wore a flared neutral trench coat while visiting Northern Ireland.
The dashing couple matched in navy blue suits while visiting an athletic track in Darwen, England.
Kate and William visit their Alma Mater, St. Andrews University, for its 600th anniversary celebrations.
Kate wore all shades of neutral to launch a new RNLI lifeboat in the chilly February weather.
The couple attended a Christmas "Spectacular," Kate dressed in contrasting black and white with a bold necklace.
The couple looked lovely and happy as can be!
For Kate and William's official engagement photos, she chose a white Reiss dress.
A royal engagement! Kate's navy Issa dress from her engagement photo is one of the most sought-after dresses she's worn.
Kate and Wills attend a friend's wedding, Kate wearing a bright silk dress with a black jacket and accessories.
Kate chose a belted teal sundress and leather bag for the Chakravarty Cup Polo Match.
Kate wore a stunning blue patterned Jane Troughton coat to a friend's wedding, paired with a Jane Corbett fascinator and black court shoes.
Kate wore skinny jeans and a leather jacket to a charity Polo match in which Prince William and Harry were playing.
Kate attended the Day-Glo Midnight Roller Disco in London, supporting an Oxford charity.
Kate channeled the '60s in this mod-inspired dress while out in London.
Kate looked lovely at Lady Rose Windsor's wedding, wearing a pop of color and print with black accessories.
Kate wore a pretty white Issa sundress with a cardigan to the Wimbledon tennis championships.
Always there to support, Kate watched Wills and Harry play in a charity polo match.
Kate attended the Most Noble Order of the Garter service, standing with Camilla, Duchess of Cornwall in contrasting black and white.
Kate in her go-to casual look: jeans and a jacket.
Kate with Prince William after his graduation, now a Royal Air Force pilot, wearing a pretty peacoat.
We love that Kate paired navy blue with black -- a look that the fashion-savvy know is super chic, but many would be afraid to do.
Kate attended an afterparty following the opening night of Afrika Afrika, wearing an animal print dress.
Kate attended another book launch, dressed in a simple cap-sleeved dress.
Wearing a vest over long sleeves, Kate and the rowing team practice for the Charity Boat Challenge.
Sporty-chic Kate took part in a training session with the Sisterhood Cross Channel rowing team.
Looking nautical in stripes and wedges, Kate was spotted in London.
Kate attended the Concert for Diana in London, wearing a white trench and black heeled boots.
Kate smiles in a casual top and jeans in London.
The Middleton sisters looked lovely at a book launch party in London.
Kate wore a sweater and pencil skirt with boots to the Badminton Horse Trials, mastering that transitional time when Spring has a chill in the air.
Kate wore a 60s-inspired dress out and about in London.
Kate and Pippa watched William play rugby in casual jeans and boots.
For the next day of the festival, Kate went for a mix of blues and browns, wrapping it up with a pretty scarf and beret.
Back to her classic, almost professional, duds, Kate wore a matching deep green skirt and coat to the Cheltenham Festival.
Seen leaving the venue Boujis, Kate looked classic in a shimmering black jacket.
Showing off some not-often-seen skin, the now Duchess was out on the town with friends.
Kate wore this casual black and white patterned dress, arriving home from work.
Kate wore a red Armani coat to the Sovereign's Parade at the Royal Military Academy.
Kate rocked white jeans and a simple cardigan at the Beaufort Polo Club.
Dressed in casual summer whites, Kate attended the Rundle Cup Day with Chelsy Davy (Prince Harry's former girlfriend) and William's cousin Zara Phillips.
Kate wore one of her favorite silhouettes, a simple wrap dress, for a Polo match.
Kate dances with a friend at a pre-Wimbledon party, dressed in a dark floral dress.
Kate wore red and white polka dots to the Chakravarty Polo match, completing the look with strappy wedges and classic sunglasses.
Kate wore a floral dress and pink jacket to a store opening, letting her bangs fall to a fringe.
Kate attended the Boodles Boxing Ball, dressed in bright blue to support the sports charity Sparks.
Kate looked lovely in a long cream coat and fancy fascinator at a friend's wedding.
Wills made Kate laugh after she and her sister watched him play in a field game at Eton College.
Kate wore flat boots, a long coat and Russian-style fur hat at the Cheltenham Festival with her sister Pippa.
Kate and her mother, Carole Middleton, attended the Spirit of Christmas Shopping Festival in London, Kate wearing jeans and a light blue blazer.
A casual Kate out and about with her father, graduation weekend.
Kate, dressed in a casual sweater with a brown jacket, wore her hair up for the Gatcombe Horse Trials.
Kate Middleton and Prince William on the day of their graduation ceremony at St. Andrews University.
Kate at her graduation from St. Andrews, where she met Prince William.
Kate attends the wedding of a friend, wearing a lace-patterned black and white skirt with a complimentary jacket and fascinator.
Kate skis in the Klosters with William and family.
Kate with sister Pippa and Father Michael in Jerash, Jordan. The Middleton Family moved to Amman, Jordan for two and a half years.