Homarus gammarus, known as the European lobster or common lobster, is a species of clawed lobster from the eastern Atlantic Ocean and the Mediterranean Sea.

Homarus gammarus is a large crustacean, with a body length up to 70 centimetres and weighing up to 5–6 kilograms, although the lobsters caught in lobster pots are usually 23–38 cm long and weigh 0.7–2.2 kg (1.5–4.9 lb). Like other crustaceans, lobsters have a hard exoskeleton which they must shed in order to grow, in a process called ecdysis. This may occur several times a year for young lobsters, but decreases to once every 1–2 years for larger animals.

The first pair of pereiopods is armed with a large, asymmetrical pair of feet. The larger one is the "crusher", and has rounded nodules used for crushing prey; the other is the "cutter", which has sharp inner edges, and is used for holding or tearing the prey. Usually, the left claw is the crusher, and the right is the cutter.

The exoskeleton is generally blue above, with spots that coalesce, and yellow below. The red colour associated with lobsters only appears after cooking.This occurs because, in life, the red pigment astaxanthin is bound to a protein complex, but the complex is broken up by the heat of cooking, releasing the red pigment.

The noticeable difference between the red lobster and the common lobster is in the claws, the claws of the common lobster are so full of delicious meat which the red lobster doesn't have.