Tennis ace Serena Williams shows off her bootylicious behind as she runs quarter marathon.

We always thought Kim Kardashian was the queen of the bootay.
But it looks like the reality queen has some serious competition from tennis ace Serena Williams.

The stunning sportswoman spent Sunday morning running a quarter marathon in Miami Beach.
The star wore a pair of very tight shorts, and a Nike tracksuit top for the sporting event, leaving ALL her curves on show.Serena tied her hair up in a ponytail and listened to her music through a pair of red headphones.