Will an iPhone purchased in the USA work in Australia?

LTE may not match up so could be 4G problems.

But the real issue: the warranty is ONLY valid in the country of sale, the US. So if anything goes wrong Apple in Australia will not touch the iPhone. And Apple US will not accept shipment from outside the country so you have to physically bring it back to give it to Apple for service.

Greetings,

Will it function as normal when I return to Australia?

If you purchase an unlocked iPhone you can insert a SIM card for your Australian wireless carrier, and it should work. I'd verify with your carrier that they support the iPhone and 4G/LTE data services on iPhone (if they don't then you'll have slower data connections).

Also, is it true that if I have any problems with the device and it is within warranty, will I have to return it to the United States in person?

No. iPhones purchased in the U.S. can be serviced in Australia.

Hope that helps and safe travels to you,

Madison

Provided you purchase a SIM card from an Australian cell phone company & use their network then, yes, the phone should work in Australia. It's not necessary to use a LTE network when using an iPhone abroad. I've used my iPhone in China, & they don't have LTE networks there. Just get a SIM card from an Australian company when you get there or purchase an international SIM card (from a company such as Telstra, although this is more expensive).

I don't see a US restriction in that link. Maybe I'm missing it.

There is this line:

"...available service options dependent on country in which service is requested and may be restricted to original country of sale."

"May" is the key.

US iPhones cannot be serviced in some regions. Australia is one of the countries where service is possible. I only know that because I've been there and had a repair. I don't see the specific countries where service is possible documented anywhere, but one could contact Apple to verify before traveling I suppose.

Cheers,

Madison

This has been debated over and over for years, and so far, no one has succeeded in getting a US phone serviced anywhere but the US, nor the other way around.

Apple has consistently interpreted may to mean will be restricted.

Anyone who wants to buy in the US to supposedly save money and take the iPhone elsewhere is taking a very expensive risk.

Read the short form of the warranty: https://manuals.info.apple.com/MANUALS/1000/MA1705/en_US/iphone_6plus_info.pdf and note that Apple does limit the service support for US-purchases to ONLY the US.