Sagartiogeton undatus, or small snakelocks anemone, is a species of sea anemone in the family Sagartiidae. The species was originally described by Otto Friedrich Müller in 1778

Distribution: Sagartiogeton undatus is found on all British coasts and is widespread throughout western Europe from Scandinavia to the Mediterranean.

 Sagartiogeton undatus has a base with a diameter of up to 60 mm and can grow to a height of 120 mm or more.