The flag of Saint Helena, Ascension and Tristan da Cunha consists of a blue field with a Union Jack in the top left corner and the coat of arms of the territory centered on the right half of the flag. The coat of arms features a shield depicting a sea anchor and a rocky coast, beneath a Saint Helena plover bird, atop a helmet and above an heraldic motto scroll bearing the words "Loyal and Unshakeable". The ratio of the flag is 1:2.

The color codes for the flag are as follows:

• Blue: Pantone 286C / RGB 0, 33, 71 / CMYK 100, 54, 0, 72
• Red: Pantone 186C / RGB 213, 43, 30 / CMYK 0, 100, 87, 16
• White: Not applicable; the white areas of the flag are simply uncolored.

There are no specific geometric properties or measurements provided for this flag beyond its aspect ratio of 1:2.