Birthplace: New York City, U.S.
Nicholai Olivia Rothschild (née Hilton; born October 5, 1983) is an American businesswoman, socialite, model and fashion designer. She is a member of the Hilton family by birth, and a member of the Rothschild family through her marriage to James Rothschild, a grandson of Victor Rothschild, 3rd Baron Rothschild, in 2015.Hilton was born in New York City and raised in Los Angeles. She is the daughter of Richard Hilton, a hotel heir of the Hilton family who works as a businessman in real estate and Kathy Hilton (née Avanzino), a former actress and half sister of Kim and Kyle Richards. Hilton was named for her great-uncle, Conrad Nicholson Hilton, Jr. She is the second of four children: she has an older sister, Paris Whitney Hilton (born 1981), and two younger brothers, Barron Nicholas Hilton II (born 1989) and Conrad Hughes Hilton III (born 1994).
Hilton was raised Roman Catholic. She has Norwegian, German, Italian, English, Irish, and Scottish ancestry. Hilton graduated from Convent of the Sacred Heart, an all-girls Catholic school on the Upper East Side, in 2001. She took courses at Fashion Institute of Technology and Parsons The New School for Design but does not have a degree.
In 2004, Hilton launched her own clothing line. She also designed a line of handbags for Japanese company Samantha Thavasa. In 2007, she started her second line, Nicholai, at a higher price point. Nicholai held its fashion show for the spring/summer 2008 season on September 9, 2007, in New York City during Mercedes-Benz Fashion Week. In 2014, Hilton launched a 10-piece collection with eLuxe. She designed each piece as a reflection of her personal style and named all products for the women in her family, who embody the style of each piece.
In 2010, Hilton launched a line of jewelry. The pieces are fashion jewelry and in an Art Deco style, averaging around $200 per piece.
In 2015, she launched a capsule collection of handbags as part of a collaboration with Linea Pelle. Hilton said she was approached by Linea Pelle "to make a capsule collection and I really wanted to have it be classic. As in I didn't want to make these super trendy bags that would be out of style next season."
In August 2017, Hilton announced her collaboration with Tolani for a Mommy and Me capsule collection. The collection launched in stores in spring 2018. 
In 2005, Hilton was the face of Australian underwear line Antz Pantz alongside Kimberly Stewart. Stewart remains contracted, but Hilton has been replaced by Australian model Megan Maitland. Around this time, Hilton modeled for the cover of Lucire for its New Zealand and Romanian editions.
In 2006, she entered a partnership to open two Nicky O Hotels, the first in Miami and the second in Chicago. That same year, Hilton sued her partner in Federal Court in Los Angeles for damages and to seek an injunction against his use of the name. On February 12, 2007, Hilton was sued for breach of contract by her partners.
In 2014, Hilton published her first book, 365 Style. According to the author, the book "offers a simple method that helps girls identify the staple pieces that work best for their lifestyle, encourages them to stay true to their own tastes, and most importantly shows them how to have fun with fashion every day of the year." 365 Style was published by Harlequin, a subsidiary of HarperCollins.
In 2015, Hilton collaborated with Smashbox, the cosmetic brand owned by Estée Lauder Companies, to create a cosmetic line consisting of three limited-edition cat-inspired makeup kits (one for each of her favorite cities: New York City, Los Angeles and London).
She has supported a range of charitable organizations, including Starlight Children's Foundation, Make-a-wish Foundation, Race to Erase MS and Union Rescue Mission.
At 2:30 a.m. on August 15, 2004, Hilton married childhood friend and businessman Todd Meister at the Vegas Wedding Chapel in Las Vegas, Nevada. The marriage was annulled less than three months later, with Hilton and Meister explaining they traveled apart often and had married "on a whim".
In 2011, Hilton began dating financier James Rothschild (born 1985), a member of the Rothschild family and only son of Amschel Rothschild, after being introduced at James Stunt and Petra Ecclestone's wedding. On August 12, 2014, while on vacation at Lake Como in Italy, Hilton became engaged to Rothschild.
On July 10, 2015, the couple married at The Orangery in Kensington Palace Gardens in London, England. Hilton wore a $77,000 Valentino Haute Couture gown. Her sister, Paris, served as maid of honor. The couple honeymooned in Botswana. They have two daughters: Lily Grace Victoria (born July 2016) and Teddy Marilyn (born December 2017).
Nicky Hilton supports the following charitable causes: Multiple Sclerosis, Cancer.