There is a report of a Giant Pacific Octopus weighing up to 600 pounds even though that might be questionable

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https://en.wikipedia.org/wiki/Giant_Pacific_octopus

However, a number of questionable size records would suggest E. dofleini is the largest of all octopus species by a considerable margin,^[7] including a report of one up to 272 kg (600 lb) in weight with a 9-m (30-ft) arm span.^[8] Guinness World Records lists the biggest as 136 kg (300 lb) with an arm span of 9.8 m (32 ft).^[2][9] A UN catalog of octopuses sizes E. dofleini at 180 kg (396 lb) with an arm length of 3 m (9.8 ft).^[10]