Konta had never even made the main draw in Melbourne before this year but, incredibly, she now stands just two wins away from the title after beating Zhang 6-4 6-1.
The British number one will next face world number six Angelique Kerber, who had earlier beat Belarusian Victoria Azarenka in straight sets.
Kerber will represent Konta’s toughest test so far but after beating seven top 20 opponents since last summer, including Venus Williams in round one, anything is possible.
She is the first British female in a grand slam semi-final since Jo Durie lost in the last four at the 1983 US Open and the first at the Australian Open since Sue Barker in 1977.
The final point was a moment of fortune, as the ball struck the net and dropped the other side, but this is no fluke for Konta, who has backed up her breakthrough run to the last 16 at the US Open in September.
“She definitely didn’t make it easy for me today, every time I got ahead she was there,” Konta said.
“Unfortunately I won it on that let cord, I’m not that proud of that, but I’m happy I fought on every point.”
This was billed the battle of the under-dogs, with Zhang coming through qualifying before winning her first ever grand slam match against world number two Simona Halep in the first round.
The result would be decided as much by who better handled the occasion as who struck the stronger ball, but Konta did both, overcoming some jitters at the end of the first set to seal another convincing victory.
“I haven’t spoken to mum and dad yet but I’m pretty sure they have jet lag because of the time difference,” Konta said. “They’ve been staying up at all times.”
Both players looked nervous as they frantically bounced about for the pre-match coin toss but it was Konta who settled fastest, out-powering her opponent for the early break.
Zhang was too often tentative from the baseline and Konta capitalised, dipping in a well-placed lob to lead 3-1 and then unleashing a thundering backhand return for 5-2 and the double break.
The eighth game, however, saw a shift in momentum as Zhang, perhaps loosened up by her deficit, swung more freely while Konta, with the set in her grasp, grew tight.
One double fault chucked away a third set point and then another surrendered the break as Zhang pumped her first, injected with hopes of a comeback.
She held for 5-4, throwing it over to Konta to serve out for a second time and again the Briton struggled to take advantage.
Zhang pummelled a brave backhand winner to save set point number four and then a forehand into the net saw a fifth drift away.
But Konta’s booming first serve came back to her just when she needed it most and a swinging one down the middle dragged her over the line as she finally closed out the set.
A break each at the start of the second kept things tight but, as in the first set, Konta surged into a 3-1 lead with the more assertive style from the back.
A limp drop-volley from Zhang gifted away the double break and a 5-1 lead, leaving the Briton just one game away from the last four.
Two match points came and went, but the resistance was temporary, as a lucky let cord ensured Konta’s remarkable run continues.