Coco says she's the last person standing for U.S. women's tennis ... everyone else on her team has bailed from the Village, because the living conditions she says are ridiculous.

According to Coco, “10 girls, two bathrooms. #olympicvillage,” the 20-year-old posted on TikTok. On the bright side, Coco reflected, "All the tennis girls moved to a hotel except me. So now just five girls, two bathrooms."

The conditions, she says, are like packing sardines into a can, and most of her teammates just couldn't take it.

For perspective, there are more than 14,000 Olympians who are calling the Village home for the next 17 days ... suffice it to say, it's a lot.

There were other complaints ... a couple of Olympians say the Olympic Village has "anti-sex" beds ... with cardboard mattresses.