Overseas marriages (and divorces) are recognized here. If you satisfy the ground for divorce here (irretrievable breakdown evidenced by 12 months separation) and the jurisdictional requirements, you can apply for a divorce here. The other party does not have to be in Australia. However, some complications may arise. The marriage certificate will have to be translated if it is not in English. There may also be problems serving documents on the other party overseas. In those cases, you will probably need legal advice.