Shortly after noon AEDT on Thursday, the benchmark S&P/ASX200 index 81.2 points, or 1.04 per cent, to 7,900.5, surpassing its previous intraday high of 7,853.1 set on March 8.
The broader All Ordinaries had gained 80.1 points, or 0.99 per cent, to 8,153.7.
Barring a dramatic afternoon collapse, Thursday will be the fifth time the Australian market has closed at an all-time high this year. Before that it hadn't done so since August 13, 2021.
With a few hours of trading left, the ASX200 was on track to finish the quarter up 4.0 per cent and the month of March up 2.6 per cent, its fifth straight month of gains.
For the holiday-shortened week it was up 1.6 per cent, its fourth winning week out of the past five.
Every sector except tech was in the green at midday.
Mining was the biggest gainer, rising 1.7 per cent. BHP was up 1.8 per cent, Fortescue had climbed 1.0 per cent and Rio Tinto had advanced 1.5 per cent.
All four of the big retail banks were in the green, with ANZ, NAB and Westpac all up 0.4 per cent while CBA had edged 0.1 per cent higher at $120.10.
The Australian dollar was buying 65.22 US cents, from 65.27 US cents at Wednesday's ASX close.
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