Lady Gaga Belts Out Frank Sinatra Hits During Surprise Performance at Hollywood Cocktail Bar -- Watch!

The 'Born This Way' singer is a big fan of Ol' Blue Eyes.

Lady Gaga jazzed it up on Thursday night. 

The "Born This Way" singer made a surprise appearance at the Black Rabbit Rose restaurant and lounge in Hollywood, where she took the stage to perform a couple of Frank Sinatra hits. 

An eyewitness tells ET that Gaga performed with the live band at the venue; she first started with Sinatra's "Call Me Irresponsible" before delivering a mesmerizing performance of "Fly Me to the Moon." 

"My whole life, you know, I've been called irresponsible," she told the audience before her first performance. "It doesn't make me so mad because it's kind of true... and I like to hear the truth."

The Oscar winner, who stunned in a black leather dress and a matching fur coat, was seen sitting in a booth with Jeremy Renner at the venue, according to ET's eyewitness. The Black Rabbit Rose puts on shows every Thursday, organized by Limp Bizkit's Fred Durst. 

See Gaga in action in the video player above, courtesy of Wes Cole (@officialwesco) and featuring drummer Tyler Hammond (@notmychair). Check out more clips of her performance below. 

Thursday night's surprise performance isn't the only time Gaga has spent time with her fans lately. The 32-year-old artist recently revealed that she's been sneaking into theaters to watch her and Bradley Cooper's movie, A Star Is Born

“I’m squatted in the back with the popcorn, like, hiding and then I sneak [out] 30 minutes out because the end of the movie is so sad that I can’t take it," she shared during a February appearance on Jimmy Kimmel Live. "So I’m just, like, crying with my popcorn." 

See more on Gaga in the video below. 

Reporting by Nikki Snook