Prostanthera hirtula, commonly known as hairy mintbush, is a shrub that is native to south-eastern Australia. It has a spreading habit, growing to between 0.4 and 2 metres high. The leaves are 10 to 30 mm long and 1.5 to 6 mm wide. The flowers are dark mauve and appear in spring. The species was formally described in 1870 based on specimens collected at Mount Buffalo and Mount Disappointment by Ferdinand von Mueller and in the Grampians by Carl Wilhelmi. It occurs in New South Wales and Victoria.