The lesser octopus is more often found around the Scottish coast and west coast of England, according to experts.
They were found metres from the water's edge at neighbouring beaches along Heacham, near Hunstanton, on Tuesday.
"We can only speculate on why they were on the beach. It really is a mystery," said rescuer Kieran Copeland, of Hunstanton's Sea Life Sanctuary.
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The creatures, which can live in water up to 1,000m (3,280ft) deep, unlike common octopuses, are now being cared for by sanctuary staff.
50cm
The average length of an octopus mantle (body)
Eats small crabs and shellfish
Normally found in the Mediterranean Sea and off North Africa
Sightings in Great Britain usually around the Scottish and west coast
Can live at depths of up to 1,000m
Sanctuary supervisor Mr Copeland said: "It is very rare to come across a single stranded octopus, let alone two.
"They have a short lifespan of around three years.
"It may be that these are elderly octopuses which have crawled ashore to die, but we hope not."
He was at the beach after being called to the first octopus, when the centre was alerted to a further discovery on the next beach along.
The first creature was found by Sue Bailey, 62, of Irthlingborough, Northamptonshire, who was visiting the beach.
"I've found all sorts down there in the past and even rang the sanctuary six months ago about a seal pup I came across, but this was the first octopus," said Ms Bailey.
Both creatures have been put in quarantine tanks out of public view, but it is hoped they may go on display once they have proved fit and healthy.
Two octopuses have been rescued after "mystery" strandings on beaches in Norfolk.