I have read many rumours and seen a few hokey documentaries that Australia 'might' have been visited by other cultures long before the initial Dutch East India Company voyages and the theory of Portuguese discovery.
Is there any actual proof that this is anything more than a theory?
We don't now that much about Australia before Captain Cook because the aborigines were a prehistoric people. Egyptians almost definitely did not reach Australia. With ancient Egyptian technology, they could not even have reached the Maldives, much less India. However, there is a good chance other cultures did reach Australia. The trepangers from Sulawesi definitely had an impact upon the Yolngu people of the Northern Territory because the Yolngu language contains words like rupiah "money", jama "work", and balanda "white person" that are cognates with the Makassarese language. The Makassarese theory is the only widely excepted theory, but others claim (with spotty evidence) that China, India, or Japan contacted Australia before the Europeans.
TL;DR
Almost definitely, but not the Egyptians.
http://www.australiaforeveryone.com.au/discovery/muslims.htm
This is one website I have found, I can't find the other source just yet, am still looking, this one is just the first in my quick search.
MY BAD! It was the Wessel Islands, http://www.sodahead.com/united-states/ancient-african-coins-that-could-change-history-of-australia/question-4017987/?link=ibaf&q=&esrc=s first article that mentions it. 12th century coins dug up by soldier stationed there in WWII.