Robert Pattinson and may be dating, the rumors say. The two have hung out two times in three days...which is kind of a lot.

Sia jokingly posted a nip-slip photo from their date to her Twitter (above), saying "Best photo of me I've ever seen."

Sia and Robert Pattinson are both stars...but Sia, 37, is a lot older than 23-year-old Robbie. Cougar!

The two were seen out on the town at concerts and going for drinks...and they looked very, um, friendly.

However, a new report casts doubt on the idea that singer Sia and Robert Pattinson are dating. As in, well, they're officially denying it, or it's all media hype, or both.

Aaand at that news, Kristen Stewart has taken the boxcutter away from her wrist.

The two were spotted out for drinks at Soho House after they attended a Jay-Z and Justin Timberlake concert.

A source close to both of htem said that there is "definitely nothing romantic" going on...they just have mutual friends.

Robbie, Sia, and three other friends were out for drinks in a low-key setting. Robbie was wearing a red flannel jacket, and Sia wore white. An eyewitness confirmed that the two seem to be pretty chill, not romantic. The insider said Robie was "was equally engaged in a conversation with the entire group of people."

"Nothing about Rob and Sia came across as romantic," the eyewitness added.

Also, Sia has identified as bisexual in the past, but generally dates women....making the idea of hooking up with a dude not unheard of, but unlikely.

In fact, source say this isn't the first time they've hung out-they're just friends.

Robsten still seems to be a thing of the past, though.

Oh, and last time they got together, for the Justin Timberlake and Jay-Z show, Sia didn't wear a bra. We're not sure if that's a flirty move, a forgetful move, or a lesbian move. Time will tell.