What is Ivy League in Australia?

Excuse me, could you possibly enlighten me on the concept of an "Ivy League" in Australia? I'm aware of the prestigious Ivy League universities in the United States, but I'm intrigued to know if there's a similar esteemed grouping of institutions in Australia, and if so, what criteria define their membership and reputation in the academic realm? Are these universities renowned for their rigorous academic standards, research excellence, or perhaps a unique blend of both? I'm eager to gain a deeper understanding of this notion as it pertains to the Australian educational landscape.