Before you start

Unlocked handset
Passport
An Australian address — your hotel or temporary accommodation is fine
To be physically in Australia, if activating online with a foreign passport

Step-by-step

1
Pick a network, then pick a reseller on it
Telstra has the widest rural coverage and the highest prices; Optus and Vodafone are cheaper and perfectly good across Sydney. Resellers run on these same networks for substantially less — worth knowing before paying a premium you don't need in a dense city.
OnlineWho: You
2
Buy a starter SIM or eSIM
Available at the airport, supermarkets, post offices and phone shops. An eSIM can often be bought online and provisioned without collecting anything physical.
In personWho: YouTypically AUD 10–40 for a starter pack including initial credit
3
Activate with identity verification
Activation is done online or by phone and requires identity documents. A foreign passport is an accepted document; if you're using one to activate online, you must be physically in Australia at the time.
OnlineWho: YouUsually minutes, occasionally a few hours
4
Move to postpaid later, if you want a handset plan
Postpaid contracts generally require a credit check and often an Australian bank account and address history. Most newcomers stay on prepaid for the first few months by necessity rather than choice.
OnlineWho: You

Documents you’ll need

Passport, with a valid Australian visa
Australian address
Australian bank account and credit history, for postpaid plans only

Things most newcomers don’t know

You must be in Australia to activate online with a foreign passport.

This rules out the tidy plan of activating your Australian number before you fly. Buy the SIM in advance if you like, but expect to complete activation after landing.

Source: Carrier activation requirements

The resellers use the identical network for a fraction of the price.

In a city as well-covered as Sydney the premium networks buy you very little. Newcomers routinely overpay for months before discovering that the cheaper brand on the same towers would have been indistinguishable.

Source: community-reported, widely corroborated

A prepaid number is enough to unlock the rest of your setup.

Bank verification, myGov, rental applications and delivery services all want an Australian mobile number. Getting any number on day one removes a dependency from every other task on your list.

Source: community-reported

Common mistakes to avoid

Expecting to activate from overseas on a foreign passport — you can't.
Signing a 12- or 24-month postpaid contract before you know which suburb you'll live in.
Assuming the most expensive network is necessary in metropolitan Sydney.
Buying an airport starter pack at a premium when the same SIM is cheaper at any supermarket.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.