When Prince Harry and Ms Meghan Markle stepped out for the first time publicly after getting engaged, Ms Markle wore a white wrap coat, with an oversized collar, which was cinched at the waist with a knotted belt.
The Canadian label which created it, Line, saw it sell out quickly. Its website in some parts of the world also crashed due to high traffic.
Here are five other high profile individuals who gave fashion brands a boost with their star power.
1. Prince George
The young prince wore a two-tone red and blue checked shirt during the royal family's trip to Poland in July this year.
The shirt was by Spanish brand Tizzas, and in just 24 hours, the shirt was sold out on the website of its main retailer, Spanish department store giant El Corte Ingles.
The garment is made from 100 per cent cotton.
2. Ho Ching
When Prime Minister Lee Hsien Loong went to the White House in August last year, his wife Madam Ho Ching carried a dinosaur-motif pouch designed by a 19-year-old Pathlight student.
It led to a surge in sales of the accessory, with a note on Pathlight's Art Faculty website saying the product - the "Dino Silhouettes" pouch selling for S$14.80 - was low in stock due to overwhelming response.
3. Kate Middleton
In January 2015, the Duchess of Cambridge visited a primary school in the Notting Hill area of London, wearing a £450 (S$807) Madderson London Naomi frock.
The then-pregnant royal's fashion choice triggered an online rush to the brand's website to grab the outfit, leading to the website crashing.
The very next day, she wore a £50 shirt dress from Hobbs to visit foster carers in North London, and that too sold out quickly online.
When visiting Singapore in 2012, the Duchess of Cambridge wore a patterned skirt by local brand Raoul, which promptly sold out. Within a 24-hour period, Raoul's website traffic reportedly increased from 355 to 2,596 page views. One skirt was even sold for US$1,000 on eBay the day after the Duchess wore it.
4. Michelle Obama
In the aftermath of Barack Obama's presidential election victory of 2008, his wife Michelle went on The Tonight Show With Jay Leno, dressed in a J. Crew ensemble of a US$148 (S$199) pencil skirt, a US$148 yellow and brown tank top and a US$118 yellow cardigan.
Interest in her outfit grew, with the jcrew.com website dedicating a page to promoting the pieces from Mrs Obama's outfit.
J. Crew said it was pleased with sales, but declined to reveal sales figures.
5. Pippa Middleton
The younger Middleton sister attended a party in London in May 2013 wearing a £285 summer dress by British designer Tabitha Webb.
In a few days, the garment was sold out on my-wardrobe.com.
It was perhaps a blessing in disguise because for each dress sold, 30 per cent of proceeds went to charity.