It's been a momentous day for the Australian share market and ASX 200 shares this Wednesday. Yesterday afternoon, the S&P/ASX 200 Index (ASX: XJO) closed at 9,022.3 points. But investors evidently decided that wasn't good enough. At market open this morning, investors pushed the index higher, into uncharted territory. At the time of writing, the ASX 200 is sitting at 9,123.5 points, up a robust 1.12%, after hitting 9,130.3 points earlier this afternoon.
That's a new all-time record high for the ASX 200.
Today's gains put the ASX 200 up a healthy 10.5% over the past 12 months and 4.5% year to date in 2026 thus far. That's a stunningly successful start to 2026. The index is also up an even more impressive 4.8% since 6 February.
But let's talk about which ASX 200 shares are responsible for today's latest high.
Of course, the ASX 200 comprises 200 individual stocks. So on one level, this is a group effort. However, some ASX 200 shares are more equal than others. Like most indices, the ASX 200 is weighted by market capitalisation. This means the largest shares have a greater impact on the index than the smaller ones.
Image source: Getty Images
Which ASX 200 shares are responsible for today's record high?
As such, there are just a handful of ASX 200 shares that are mostly responsible for today's new high. It might be tempting to single out the ASX 200's largest single constituent, Commonwealth Bank of Australia (ASX: CBA). Yes, CBA's 0.7% gain would be pulling its weight for today's fresh highs. And its near-20% rebound over the past month has certainly gotten the index to where it is today. But CBA is still not back at its all-time highs of over $190 a share.
Instead, it's BHP Group Ltd (ASX: BHP) that stands out as the biggest backer of the ASX200's fresh high. BHP, the mining giant that is now the ASX 200's second-largest holding, has blazed to a new record high of its own today. The Big Australian is presently up a massive 32.5% over 12 months, at $56.12, after hitting $56.36 earlier this morning.
We have also seen National Australia Bank Ltd (ASX: NAB) and Westpac Banking Corp (ASX: WBC) clock new record highs of their own today. NAB and Westpac are currently the third- and fourth-largest stocks on the ASX 200, so their new highs would also be playing a major role in today's proceedings.
All in all, today's new milestone for the ASX 200 just reinforces how dominant bank shares and mining stocks remain in the broader ASX 200 Index. Not that too many investors will be minding right now.
