The Gold Coast local, who is ranked no. 240 in the world, took just under two hours to defeat Croatia's Donna Vekić 6-4 4-6 6-1. 

Vekić is ranked 220 spots above the Australian but was clearly rattled and frustrated during the three-set thriller on Court 2. 

"It's so surreal that was just such a blur but all I know is that I fought for every single point and left it all out there," Birrell said.

"I use the energy from the crowd and I'm just so excited that I get to play again."

It is the second time Birrell has beat a seeded player this summer, having ousted world number 10 Daria Kasatkina at the Brisbane International.

Birrell was able to take the opening set after breaking in the ninth game but the Croatian went on to break twice in the second. 

However, the 20-year-old was able to claw her way back into the set winning three straight games to bring it to 3-5 but it was a bit late and it was headed to a third. 

Birrell took her momentum and won five straight games in the third, much to the disbelief of the commentary team. 

Taken by Ben Southall (@bsouthallau)

Frustration was written across Vekić's face and when she threw her racquet on the ground for a second time, her composure was all but gone. 

She was able to salvage a game point before the young Australian served for the game. 

However, there were some nervous moments for Birrell as she had a double fault on her open serve. 

"There were so many things going through my head, I just had to bring myself back to the present," she said. 

Next up is either world no. 2 Angelique Kerber or Brazilian Beatriz Haddad Maia.