Freshly-minted Australian under-18 100m record holder Leah O’Brien hopes the best is yet to come after shocking herself to break a 57-year milestone in Perth.

The 17-year-old snapped Australian Olympic legend Raelene Boyle’s long-standing Australian record on Tuesday, lowering the mark by 0.06 with a sizzling run of 11.14.

Remarkably, it was a time just 0.04 seconds off the national record, set by fellow young gun Torrie Lewis.

Know the news with the 7NEWS app: Download today

The teenager said she was still surprised at having broken the record but felt she still had room to grow; food for thought for rivals, perhaps.

“The realisation hasn’t sunk in, but overall, I had a pretty great race. The start was quite good, I executed that well, and my top-end speed was great,” she told The West Australian.

“I probably could have dipped a little bit more, I stayed up tall at the end of the race.

“It just felt like how I’m normally running. I definitely felt fast, and I could feel myself passing the other girls, but I think it was just due to having a good start.

“I didn’t have to compensate, try and make up for it, whereas normally I have to make up for having not as great of a start. I really shaved off some time with having a better start than usual.”

O’Brien will back up her efforts at the junior championships when she takes to the WA Athletics Stadium track on Saturday for the senior heats — where she may even find herself side-by-side with Lewis.

“Last year, I was actually in the open national final, so I do have some experience basically against the top girls, but I’m really excited to race against all of them again and get some more race experience,” she said.

The Perth College student admitted she did not know the record heading into the meet because she never really considered it an achievable goal.

“I didn’t even realise I broke the record because I actually didn’t know what the record was; I never even planned on breaking it,” she said.

“I knew what our state record was because I really wanted to break that, but I never imagined I’d break the national record.

“It was definitely really great conditions as well — a hot track, and it was a plus 1.7 tailwind, which is perfect, but it was just a great race for me.”

O’Brien’s time also equalled Olympic champion Sally Pearson’s best time for a 100m sans-hurdles.

“It is so weird to think about because a few years ago, I would always look up to her, and I’d be like, ‘wow, she is so fast’; I could never imagine one day, sharing a personal best time with her,” O’Brien said.

WATCH THE AUSTRALIAN ATHLETICS CHAMPIONSHIPS STARTING TODAY ON 7PLUS