The flag of Cook Islands consists of a blue field with a ring of 15 white stars located on the left-side hoist. The stars represent the fifteen islands that make up the Cook Islands. The Union Jack appears in the upper left-hand corner, symbolizing the country's historic ties to the United Kingdom. The flag has an aspect ratio of 1:2 and its geometric properties include a rectangular shape measuring 120 cm x 240 cm (or 3:5 in proportion). It uses the following color codes:

• Blue: Pantone 286 C / RGB 0, 57, 166 / HEX #0039A6
• White: No specific code

The flag was officially adopted on August 4, 1979, and is used as the national ensign and civil flag of the Cook Islands.