Plantago triandra is a species of flowering plant in the family Plantaginaceae that is endemic to New Zealand.

Plants of this species of plantain are perennial with a rosette habit, with angular-ovate leaves, tiny calyces, numerous seeds, and often sessile flowers and fruiting capsules.

[1] The holotype was collected by Sven Berggren at Kelly's Hill, Canterbury, South Island in February 1874.

[9] Plantago triandra plants are small rosettes with a primary root up to 12 mm thick, with up to 62 usually angular-ovate leaves, and with visible, short (<13 mm long), rust-coloured leaf axillary hairs in the basal rosette.

The leaf has an acute apex, and its edges are smooth, wavy or with up to 24 small to large teeth.

Each capsule has 8–42 uniform rust or brown seeds 0.5–1.4 mm long, usually rhomboid or angular-ovoid.

[12][13][14] Plantago triandra is a plantain that is endemic to the North, South, Stewart and Chatham Islands of New Zealand.

[15] Similarly, Plantago triandra was closely related to P. unibracteata in a phylogenetic study of the New Zealand species using amplified fragment length polymorphisms (AFLPs).

It was hypothesized that decaploid and dodecaploid P. unibracteata are allopolyploids that have evolved multiple times from octoploid P. triandra and another species.