The suburb is adjacent to the suburbs of Kenny and Harrison and is bounded by the Federal Highway to the east, the ACT/NSW border to the north, Horse Park Drive to the south and the Goorooyarroo nature reserve to the west.

The suburb is named after the explorer Charles Throsby who was one of the first Europeans to open up the lands west of the Blue Mountains to grazing and agriculture.

The high point of Throsby is 656 metres near 'Old Joe' Hill on the easterly arm.

The low point of the suburb when it is built is 610 metres where the creek drains towards the east.

The rock in the hills to the east (including Old Joe) is grey quartz andesite from the Ainslie Volcanics.