Heteractis magnifica, also known by the common names magnificent sea anemone or Ritteri anemone, is a species of sea anemone that lives in the Indo-Pacific area, and can grow up to 1 metre (3 feet) in diameter in the wild. It can be kept in aquaria but is considered one of the most challenging species to keep healthy. They require very strong lighting and very high chaotic flow. They will not survive in tanks with any presence of nitrites or nitrates. If they are healthy and kept well fed they will grow very rapidly. H. magnifica consumes both vertebrates and invertebrates, including fish and crustaceans.
It is often found in association with anemonefish, or clownfish, such as the cinnamon anemonefish (Amphiprion melanopus), Clark's anemonefish (A. clarkii), common clownfish (A. ocellaris), blackfinned anemonefish (A. nigripes), true clownfish (A. percula), and the pink skunk clownfish (A. perideraion). Juvenile Threespot dascyllus (Dascyllus trimaculatus) also commonly associate with this sea anemone.
H. magnifica was featured in the Pixar Animations film Finding Nemo.