The Senate is set to have equal numbers of men and women for the first time in Australian political history.
Victorian Liberal senator-elect Sarah Henderson could be sworn in as early as Thursday after being preselected by the party over the weekend.
She will replace Mitch Fifield, who has been appointed Australia's ambassador to the United Nations, based in New York.
The Victorian state parliament is expected to confirm Ms Henderson's election on Wednesday night, paving the way for Canberra formalities on Thursday pending the Senate's receipt of the paperwork.
Ms Henderson was the Liberal MP for Corangamite and an assistant minister but narrowly lost her seat at the federal election in May.
Senate President Scott Ryan said it would be a milestone for the upper house, which has 76 members.
"Equal numbers of women and men for the first time ever," he tweeted on Monday.
The first woman to be elected to the Senate was Labor's Dorothy Tangney in 1943.
Victoria achieved its first female senator in 1950, with the election of the Liberal party's Ivy Wedgwood.
