Selena Gomez surprised fans during a Rare Beauty promotional event in London on Tuesday by allowing them to stream her playing her not-yet-released single.

The upcoming song - most likely titled Call Me When You Break Up - is a duet between the 32-year-old 'Texican' pop star and Gracie Abrams, and the bouncy track was produced by her fiancé Benny Blanco.

'Oh I get so nervous!' Selena cringed while introducing the song as her fans stood nearby at Mortimer House in Fitzrovia.

'Call me when you break up / I wanna be the first one on your mind when you wake up,' Gomez sang along with the lyrics.

'I miss the way we'd stay up / We talk about forever when I'm taking off my make-up.'

The two-time Grammy nominee looked slim and leggy in a $950 red Roland Mouret 'Long Sleeve Tailoring Wool' mini-dress and matching $975 Jimmy Choo 'Ixie 80' pumps selected by stylist Erin Walsh.

Selena - who has lupus - previously confessed to LADBible as recent as November 11 that she 'doesn't even go to the gym' despite being the subject of rampant Ozempic rumors.

Hairstylist Renato Campora coiffed Gomez's sleek brunette bob and make-up artist Hung Vanngo fully contoured her glowing complexion.

'I'm so excited for you guys to share it, if you want, do whatever you want. I'm just so thrilled,' the certified billionaire gushed to her fans.

'To get the obvious statement out of the way, this song is actually about my best friend that I have in my life, so it's not about anything if you think it is. But I'm so excited for you guys to hear this album. It's been so much fun creating it with Benny and we're just going to keep, hopefully, releasing some fun stuff. I hope you all like it!'

It marked the second single off Selena and Blanco's collaborative album I Said I Love You First - dropping on March 21 - after they released Scared of Loving You last Thursday.

TikTok user @peppeperalta1 gushed in the comments: 'OMG it's a bop!'

'I'm so happy for you and the song is so good!' TikTok user @extracarolas wrote.

TikTok user @aliciaw482 commented: 'Yes! Love her, love the new songs, and more importantly I love how she is coming out and being so happy! She deserves everything!'

'Sounds like something she would release in her early career. I love it!' TikTok user @saturn.r3turns wrote.

TikTok user @cheeba__ commented: 'Put this girl on stage now!'

'Our queen is back! 'TikTok user @fefe01.1 declared.

Gomez and her three Emilia Pérez co-stars are nominated for outstanding performance by a cast in a motion picture at the 31st Screen Actors Guild Awards, which air this Sunday at 5pm PT on Netflix.

The former Disney Channel star, Zoe Saldaña, Karla Sofía Gascón, and Adriana Paz were previously awarded the Cannes Film Festival's best actress prize on May 25 for their work in Jacques Audiard's critically-acclaimed queer musical.

Selena and nine of her Only Murders in the Building co-stars will also compete for the outstanding performance by an ensemble in a comedy series trophy.

Gomez will next portray 11-time Grammy winner Linda Ronstadt in David O. Russell's untitled biopic produced by her former manager John Boylan.