Yep ... that's YouTube star Rebecca Black, best known for her 2011 earworm, "Friday" ... and we have a feeling these photos will be just as catchy for her fans.

Rebecca hit the pool at the Dream Hollywood hotel over the weekend. Apparently, she doesn't ONLY get down on Fridays. She's looking a helluva lot more grown up than the teenager most remember singing that annoying (we say that lovingly) one-off hit.