The Keeping Up With The Kardashians star and New Jersey Nets player Humphries will tie the knot at a ceremony in Montecito, as previously speculated.
A copy of the official wedding invitation, posted by E! Online, reads: "Kris and Bruce Jenner request the pleasure of your company at the marriage of their daughter Kimberly Kardashian to Kristopher Humphries on Saturday, August 20, 2011."
The guests have also been told to dress black tie.
Kardashian and Humphries personalised the invitation by including an image of two intertwined Ks to represent the first letters of their first names.
The couple became engaged in May after Humphries popped the question by spelling 'will you marry me?' in rose petals on Kardashian's bedroom floor.
Kardashian celebrated her wedding shower and bachelorette party with friends and family at Tao in Las Vegas last week, while Humphries threw a bachelor party at a nearby club.
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Watch a promo for the current season of Keeping Up With The Kardashians below: