The flag of Réunion is a rectangular shape with an aspect ratio of 2:3. It consists of two equal horizontal bands: the top one is blue and the bottom one is red. A white circle in the center of the flag contains a stylized representation of an erupting volcano in yellow, with a black outline. The diameter of the circle is 2/5 of the hoist width. The exact color codes for the flag are as follows:

• Blue: Pantone 280 C; RGB (0, 30, 76); CMYK (100, 60, 0, 70)
• Red: Pantone 186 C; RGB (206, 17, 38); CMYK (0, 100, 100, 0)
• Yellow: Pantone 116 C; RGB (255, 204, 0); CMYK (0, 15, 100, 0)
• White: not specified, but it can be assumed to be pure white

The volcano in the flag has a height of 1/5 of the hoist width, and its base is located at the center of the flag. Its shape is composed of two overlapping triangles, forming a stylized depiction of Piton de la Fournaise, an active volcano on the island.