Mattek-Sands sealed top spot after winning her 23rd WTA doubles title in Brisbane on Saturday with partner Sania Mirza.
She ended her Indian partner's 91-week reign as world number one.
"Being number one is something that you dream of from the time you pick up a racket," Mattek-Sands, whose daring outfits and knee-high socks mark her out from the crowd, told the WTA.
"You're not given number one -- you have to earn it and I feel really proud of myself for getting there."
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Mirza added: "I feel like I'm handing over the Miss World No 1 crown. Congratulations to her for becoming No 1. She has had an amazing year.",
Mattek-Sands has won three grand slam doubles titles all with Czech Lucie Safarova -- the most recent coming at last year's U.S. Open.
(Reporting by Martyn Herman, editing by Pritha Sarkar)
