Octopus tetricus, the gloomy octopus or the common Sydney octopus, is a species of octopus from the subtropical waters of eastern Australia and New Zealand. O. tetricus belongs to the Octopus vulgaris species group and is a commercially prized species. All species within the O. vulgaris group are similar in morphology. The English translation of O. tetricus (Latin) is 'the gloomy octopus'.