"Coming along, folks ... coming along," Spears wrote in the caption, alongside clips of her riding a horse and doing cartwheels in a park, all set to KT Tunstall's "Black Horse And The Cherry Tree."
"New with real representation today ... I feel GRATITUDE and BLESSED !!!!" Spears continued in her caption. "Thank you to my fans who are supporting me ... You have no idea what it means to me be supported by such awesome fans !!!! God bless you all !!!!!"
The singer added, "This is me celebrating by horseback riding and doing cartwheels today 🤸♂️🤷♀️🐎 !!!! #FreeBritney"
This is believed to be the first time the singer has publicly used the hashtag.
After she shared the post, Spears was inundated with messages of support from her fans and followers - including Ariana Grande, who commented, "YOU ARE SO VERY LOVED AND SUPPORTED."
Spears' boyfriend, Sam Asghari, commented, "Internet is about to explode #FreeBritney," and he shared the popular rallying cry in a post to his Instagram story, in pink block letters on a black background.
On Wednesday, during Spears' latest court hearing, Judge Brenda Penny granted the singer permission to hire Mathew Rosengart, a prominent Hollywood lawyer and former federal prosecutor, as her new attorney moving forward.
Legal expert Rachel Stockman spoke with ET on Wednesday and said that Judge Penny's decision to let Spears hire her own attorney is "a real gamechanger."
"Britney Spears finally gets to hire her own attorney, her own advocate to fight for her. She gets to choose someone, she gets to vet the background, and she gets to make that decision," said Stockman, president of the Law&Crime Network. "I think it's a big move and I think it's a really important one."