American citizens are required to have a valid U.S. passport to enter Australia. Americans must enter with an Australian visa or, if eligible, through Electronic Travel Authority (ETA). The ETA replaces a visa and allows a stay of up to three months. It may be obtained for a small service fee at http://www.eta.immi.gov.au. Airlines and many travel agents in the United States are also able to issue ETA’s. Please note that American citizens, who overstay their ETA or visa, even for short periods, may be subject to exclusion, detention and removal.