This is a list of appointments to the Australian Senate, filling casual vacancies, from the Senate's creation in 1901 until the present day.
Section 15 of the Australian Constitution requires the parliament of the relevant state to choose a replacement. This is done in a joint sitting of the upper and lower house (except for Queensland, which has a unicameral parliament). In the event that the state parliament is not in session, the Governor of the state (acting on the advice of the state's executive council) may appoint a replacement senator, but such an appointment lapses if it is not confirmed by a joint sitting of the parliament within 14 days.
Prior to 29 July 1977, it was an established convention that the state parliament choose (or the governor appoint) a replacement from the same political party as their predecessor. This is now a constitutional requirement.
Replacement senators for the Australian Capital Territory or the Northern Territory are chosen by the relevant territory legislature, under s.44 of the Commonwealth Electoral Act 1918. Where the legislature is not in session, the choice is made by the Chief Minister of the ACT or the Administrator of the NT. Prior to the passage of this legislation, replacement territory senators were chosen by a joint sitting of both houses of the Federal Parliament, under s.9 of the Senate (Representation of Territories) Act 1973.
Appointments marked with an asterisk (*) occurred after the election for that parliament but before the new Senate was sworn in. Party designations marked with a † indicate that the member was elected for a different party, but defected during their term. (The appointment is generally made to the original elected party or its equivalent.)