A photosynthetic pigment is a pigment present in chloroplasts or photosynthetic bacteria which provides the energy necessary for photosynthesis.

Green plants have five closely-related photosynthetic pigments (in order of increasing polarity):

• Carotene - an orange pigment
• Xanthophyll - a yellow pigment
• Chlorophyll a - a blue-green pigment
• Chlorophyll b - a yellow-green pigment
• Phaeophytin - a grey pigment

Chlorophyll a is the most common of the five, present in every plant that performs photosynthesis. The reason that there are so many pigments is that each absorbs light more efficiently in a different part of the spectrum. Chlorophyll a absorbs well at a wavelength of about 400-450 nm and at 650-700 nm; chlorophyll b at 450-500 nm. Xanthophyll absorbs well at 400-530 nm. However, none of the pigments absorbs well in the green-yellow region, which is responsible for the abundant green we see in nature.

Pigmentation varies among the different groups of algae. Of particular note are the kinds of chlorophylls present.