The division is named after
Sir Charles Mackellar, a social reformer and surgeon who served in the Senate from October to November 1903, and his daughter
Dorothea Mackellar, a 20th-century Australian
poet. The division was proclaimed at the redistribution of 11 May 1949, and was first contested at the
1949 federal election. It was first held by
Bill Wentworth, the first Minister for Aboriginal Affairs, and the great-grandson of politician and explorer
William Wentworth, one of the first three Europeans to cross the
Blue Mountains. Like most seats in northern Sydney, Mackellar was a safe seat for the
Liberal Party of Australia for the majority of its history. Prior to 2022, for all but two months of its existence, the seat was held by Liberal MPs; Wentworth briefly sat as an independent for the last two months of his term. The territory covered by the electorate had been represented by the Liberals and their predecessors for most of its history since Federation; it was part of
North Sydney before 1922, and then part of
Warringah from 1922 to 1949. In
1972, Wentworth only tallied 55.2 percent of the two party vote. This election was also the first time the Liberals had come up short of winning enough votes on the first count to win the seat outright. It would be half a century before the Liberals' hold on the seat would be seriously threatened again. Former
Speaker of the House of Representatives Bronwyn Bishop held the seat from 1994 until 2016, when she lost a preselection contest for the Liberal nomination following an expenses scandal. The Liberal Party preselected
Jason Falinski to contest the seat, who won both the
2016 and
2019 Federal elections. At the
2022 federal election, a Liberal candidate lost the election for the first time in the seat's history. Falinski lost over 11 percent of his primary vote from 2019, and was unseated by
teal independent Sophie Scamps as part of a wave of Liberal losses in wealthy metropolitan seats. In
2025, Scamps retained Mackellar with a swing in her favor of 3.9 points. Meanwhile, the Liberals set a new record low for their two-party-preferred vote against Labor in this seat. Following the election, it sits at 53.7 percent, below the 1972 result. ==Geography==