The website of British brand Goat crashed within minutes of the duchess being pictured in a dusky pink Flavia silk-crepe pencil dress.
The dress is available to buy on the website for £590.
Goat told Sky News the outfit had been tailored to perfectly fit the duchess.
The website was down for more than 40 minutes, with the brand confirming it crashed after the newly-wed was spotted wearing the luxury designer.
On retailer site matchesfashion.com, the dress is described as a “a study in the elegance of simplicity”.
The site highlights that the waist seam is “curved for an elongating effect”.
It suggests whoever wears it “save it for a special occasion”.
Jane Lewis, the founder of Goat, told Sky News: “We are delighted Meghan chose to wear Goat and it was a pleasure the make a custom dress for her.”
Goat describes the dress as “beautifully fluid and feminine… Perfect for both daytime or evening event dressing”.
The dress has contrast silk-chiffon decolletage and sleeves. It has a delicate frayed edge trim on the neckline and cuffs and is also available in black.
Goat’s website lists the dusky pink dress as available to buy in sizes between 8 and 18.
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The duchess was also pictured wearing a Philip Treacy dome hat in sinamay fabric.
A spokesperson for the brand told Sky News the price was available upon request and that it was custom-made for the duchess.