Sigaus tumidicauda is a species of alpine grasshopper, endemic to New Zealand.

[2] Like all of New Zealand sub-alpine and alpine grasshoppers, S. tumidicauda has a 2- or 3-year life cycle.

Sigaus tumidicauda prefers alpine tussock grasslands between 1,300 and 1,700 metres (4,300 and 5,600 ft); it can, however, be found as low as 700 metres (2,300 ft) near the Nevis River (45°08′49″S 169°00′00″E / 45.147°S 169.000°E / -45.147; 169.000 (Nevis River)).

[4] Alpinacris tumidicauda is sister to the widespread species Sigaus australis.

[8] Sigaus tumidicauda is micropterous (small-winged), with wings measuring between 2 and 4 millimetres (0.079 and 0.157 in), making this species flightless like most New Zealand grasshoppers.