Short answer: there isn’t one single “best” — it depends on what you want. If you mean “best overall for Australians (range, delivery, returns, local focus)”, THE ICONIC is widely seen as the top all‑round online fashion destination in Australia. (en.wikipedia.org)

Quick guide by need

• Best overall (range, speed, returns): THE ICONIC — largest local selection of brands, fast delivery and easy returns make it the go‑to for most shoppers. (en.wikipedia.org)
• Best for trendy / youth styles and partywear: Princess Polly and Showpo — popular, trend‑led Australian labels aimed at younger shoppers. (Check reviews for sizing/quality on particular pieces.) (trustpilot.com)
• Best for designer / luxury: Net‑A‑Porter, SSENSE and similar international boutiques that ship to Australia. Good if you want high‑end labels. (elle.com.au)
• Best department‑store selection (brands across price points): Myer and David Jones — good if you want one site that covers mass and premium brands. (They rank highly in Australian site traffic.) (statista.com)
• Best for bargain fast‑fashion (lowest prices, but variable quality): Temu and Shein — huge price savings but be mindful of quality, sizing and longer returns/customer‑service tradeoffs. Their rapid growth is also pressuring traditional retailers. (dailytelegraph.com.au)

If you tell me your budget, style or whether you want fast shipping vs. sustainable/quality pieces, I can point you to the single best site for your needs.