The Chloroflexi (Chlorobacteria) are a class of bacteria that produce energy through photosynthesis. They make up the bulk of the filamentous anoxygenic phototrophs (formerly known as green non-sulfur bacteria), though some are classified separately as the Thermomicrobia. They are named for their green pigment, usually found in photosynthetic bodies called chlorosomes.

Chloroflexi are typically filamentous, and can move about through bacterial gliding. They are facultatively aerobic, but do not produce oxygen during photosynthesis, and have a different method of carbon fixation (photoheterotrophy) than other photosynthetic bacteria. Phylogenetic analysis indicates that they had a separate origin.