The big four bank shares make up an important part of many investors' portfolios.
These banks also have such a market dominance in the Australian economy that the performance of these stocks influences the S&P/ASX 200 Index (ASX: XJO).
Much of the focus this year was on Commonwealth Bank of Australia (ASX: CBA) shares, which hit record high after record high early in 2025.
However, today, CBA shares are tumbling 6% following the release of the bank's first-quarter update.
So, as the end of the calendar year draws to a close, here are the best and worst performing big four bank shares.
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ANZ the big winner
ANZ Group Holdings Ltd (ASX: ANZ) shares have performed the best out of the big four banks in 2025.
At the start of the year, ANZ shares were trading for $28.59 each.
Today, shares are trading hands for roughly $38.
This represents a 32.8% rise this year.
A $10,000 investment in January would now be worth a healthy $13,280.
Despite such a big rise, it seems analysts and brokers now believe it might be overvalued.
Macquarie has a neutral rating on its shares with a price target of $35, while Morgans has a price target of $33.09.
Westpac and NAB healthy risers
While ANZ has outpaced the other big four bank shares, Westpac Banking Corp (ASX: WBC) has risen 23.87% in 2025.
National Australia Bank Ltd (ASX: NAB) shares have risen a healthy 15.33%.
NAB shares have hit 52-week highs recently, and are up 20% in the last 6 months.
Despite gains for both ASX bank shares, experts seem to believe these banks are trading above fair value.
Macquarie recently placed a price target of $32 for Westpac shares, which indicates a downside of more than 20%.
The broker also recently placed a price target of $38 on NAB shares, indicating the stock is overpriced by 11.46%.
CBA falters
Shockingly, after such a strong start to the year, CBA shares have the lowest return since January out of the big four bank shares.
Including today's tumble, the CBA stock price is up approximately 6% year to date.
Australia's largest bank shares have fallen more than 14% since June, when they hit more than $191 per share.
