The Gair Affair was an episode in Australian political life in 1974, during the government led by the Labor Prime Minister Gough Whitlam. Whitlam offered the post of Ambassador to Ireland to a non-government senator from Queensland, Vince Gair, in the hope that this would improve Labor's chance of gaining a majority in the Senate at the forthcoming general election. Whitlam's plan was foiled by the Premier of Queensland, Joh Bjelke-Petersen, during what came to be known as "The Night of the Long Prawns", but the matter was overtaken by events when Whitlam decided to call a double dissolution election.

Jenny Hocking has said of the affair: "The government's attempts to effect an additional Senate vacancy through Gair's resignation was constitutionally sound, strategically brilliant and an unmitigated political disaster."

At the 1972 election, Gough Whitlam led the Australian Labor Party to its first success at the federal level in 23 years. Although another election for the House of Representatives was not due until early 1976, an election for half the Senate was required earlier. Normally, these elections are held on the same day, but they had become out of synchronisation in 1963 due to the then Prime Minister Sir Robert Menzies calling an early House election. Between 1963 and 1972, elections for the Senate and House of Representatives were held separately. The last half-Senate election was held on 21 November 1970, senators' terms commencing on 1 July 1971. Another half-Senate election had to be held in time for senators to commence their terms on 1 July 1974. Such an election could have been called for any time from early August 1973, but Whitlam was in no hurry.

Although Labor controlled the House of Representatives with a 9-seat majority, it was 5 seats short of a majority in the Senate. Consequently, Labor faced constant opposition in getting its legislation through the parliament. By March 1974, a number of bills had been twice rejected by the Senate, which gave Whitlam the capacity to call a double dissolution, in which the entire parliament would be up for election. If the government were returned, it could reintroduce the bills in question, and if they were rejected by the Senate a third time, the government could seek to hold a joint sitting of the Senate and House.

In early March 1974, however, such a course of action was not under active consideration. It was an option that had only ever been used twice before (in 1914, when the government was defeated; and 1951, when the government was returned with a reduced majority in the lower house, albeit now with a majority in the Senate) and was regarded as somewhat extreme. Also, Labor felt it needed more time to improve its electoral stocks before considering such a move. Whitlam still only intended to call a half-Senate election, even though this would continue the lack of synchronicity between the elections of the houses, something he had often deplored. In debates in parliament and in outside commentary, he often decried the fact that senators elected in 1967 and 1970 were able to frustrate the will of a government elected in 1972.

Section 12 of the Constitution provides that the writ for a Senate election in each State is issued by the State Governor.

Vincent Clair Gair was a former Australian Labor Party (ALP) Premier of Queensland 1952-57 who was expelled from his own party while in office, and formed the breakaway Queensland Labor Party (QLP), which in 1962 merged with the Democratic Labor Party (DLP). In 1964 he was elected to federal parliament as a DLP Senator for Queensland, his term commencing on 1 July 1965. He was elected parliamentary leader of the DLP immediately although it had only two members at that time (Frank McManus from Victoria was the other). He was re-elected in 1970 for a new term (1971–1977). In 1973, by which time the DLP's Senate numbers had risen to five, internal issues caused Gair to resign as leader of the party from 10 October, with McManus taking over. He had first intimated in January 1973 that he would resign as leader, but vacillated until October, when Frank McManus offered him the choice of immediate resignation or being removed by his colleagues.

Gair announced at that time that his current term as senator would be his last. In March 1974 he also complained to the ALP senator Justin O'Byrne that the DLP had treated him shabbily. He said he was thinking of leaving the Senate earlier than 1977, and suggested that he would consider accepting a diplomatic post should the government be minded to offer him one. O'Byrne repeated this conversation to his Senate Leader Lionel Murphy, who devised a plan to use Gair's disgruntlement to the ALP's advantage, which he talked over with Whitlam. The plan was to appoint Gair to an overseas post, which would require him to resign his seat in the Senate, and to arrange for this to occur before the writs for the impending half-Senate election were issued. This would have the effect of causing writs to be issued for the election of 6 senators from Queensland, not the 5 as would otherwise have been the case (at that time, each state had 10 senators, and 5 of them were elected at each half-Senate election). Gair was not the only non-ALP person in the ALP's sights: they also offered the post of Ambassador to the Holy See to Frank McManus (he refused outright); and they had been considering offering Liberal senator Peter Durack a seat on the High Court, but never approached him.