The Methylococcaceae are a family of bacteria that obtain their carbon and energy from methane, called methanotrophs.
They comprise the type I methanotrophs, in contrast to the Methylocystaceae or type II methanotrophs. They belong to Gammaproteobacteria, and are typically given their own order.
The Methylococcaceae have internal membranes in the form of flattened discs, perpendicular to the cell wall.
Some species of the Methylococcaceae have formed with certain marine mussels endosymbiotic relationships.