The singer's rumored ladylove was in the audience at his concert in Austria over the weekend.
In photos obtained by TMZ, the Bones and All actress was spotted hanging out in a special section during Styles' Love on Tour concert on Saturday, enjoying the show enthusiastically.
The outlet reports that Russell -- who was first romantically linked to Styles last month -- was dancing to Styles' songs throughout his show.
After Saturday's show, fans were stirred into a frenzy on Sunday when videos surfaced show Styles and Russell walking hand-in-hand through the streets of Vienna.
The pair went around town incognito, with Russell rocking black pants and a white T-shirt while Styles wore dark shades and a blue windbreaker with khaki shorts.
It's worth noting that one reason Styles might have been wearing shades is that his concert on Saturday was notable for more reasons than just having his supposed girlfriend in the audience.
Styles also became the latest singer to get pelted with objects hurled on stage by fans during a performance. In fact, he was hit in the eye by an unknown object -- which many fans claim was a phone.
A fan video taken of the incident shows Styles strutting down the runway with his microphone when the incident occurred. Styles covers his eye with his hand after being pelted in the face, attempting to make his way across the stage despite being briefly interrupted.
It's unclear what hit the "As It Was" singer, but it appeared to be pretty painful as he visibly grimaced, rubbing his agitated eye following the incident.
This was not the first time Styles has been hit with an object, having most recently been hit by a bouquet of flowers back in June. He was also hit in the groin with an apparent water bottle last year.
He also joins a long list of performers who have been struck while performing onstage in recent months.
Last month, Kelsea Ballerini was hit in the eye with a bracelet while performing in Idaho, and just days before that, Bebe Rexha was badly injured after a fan hurled a phone at her head, leaving her with a black eye and cut on her face.
Ava Max, meanwhile, was slapped on stage by a concert crasher, Pink was performing at London's Hyde Park when a fan threw a bag of her late mother's ashes onto the stage and Lil Nas X dodged a sex toy thrown at him during a performance in Sweden.