5-137925960DT080_1_OAK_Las_Ve.JPG4-137925960DT031_1_OAK_Las_Ve.JPGDenise Truscello/WireImage

Katy Perry wasn't the only one at the grand opening of 1 OAK Las Vegas at The Mirage last night -- Paris and Nicky Hilton were also on hand for the evening's festivities, and the ladies looked gorgeous as they posed for pictures outside the brand new hotspot.

We're not sure if Paris and Katy became new BFFs over the course of the night, but after this sweet tweet, it's definitely a possibility! "@KatyPerry looking gorgeous across the room," P gushed. "Love her hair & dress! #Stunning!" Awww!

Earlier in the day Paris spent time shopping with Nicky, and she also went to the Chanel Numeros Prives exhibit at the Wynn. "So many fashionable & interesting art exhibitions," Paris tweeted. "@KarlLagerfeld rocks!"