The tennis superstar just plunked down $6.7 million on a 6,000 square foot pad in a private gated Bev Hills community, according to Trulia.com.

The place looks AWESOME -- with 5 bedrooms, 7 baths, incredible view, dope backyard with a pool -- but still no tennis court.

As we previously reported, Williams is selling a nearby home she owns for $12 mil. She bought that place a few years back for $6 mil.

So, she flips that house -- pockets $6 mil -- and buys a new dope house for half the price?