Prostanthera sejuncta is a flowering plant in the family Lamiaceae and is endemic to a small area of New South Wales.

Prostanthera sejuncta is a scrambling, more or less prostrate, aromatic shrub that typically grows to a height of 50 cm (20 in) with branches that have spines up to 16 mm (0.63 in) long arranged in opposite pairs at right angles to each other.

[2] Prostanthera sejuncta was first formally described in 2006 by Mark Williams, Andrew Drinnan and Neville Walsh in the journal Australian Systematic Botany from specimens collected on Mount Arapiles.

[3][4] Specimens of this plant were previously included with P. spinosa, now considered to be endemic to Victoria.

[2] This mintbush grows in sandstone soils often along main creeklines near Copmanhurst in north-eastern New South Wales.