The plural of octopus is octopuses.
A cephalopod mollusk with eight arms and a soft body.
The plural form of octopus can be a contentious one. Many will swear it to be octopi or octopodes yet these are both actually incorrect.
Since the English word octopus comes from Latin it is argued that the plural for octopus should end in -i and be written octopi.
However, since the word octopus was originally derived from Greek, others argue that the word should end in -odes, making the plural form octopodes.
Ultimately English is a language full of contradictions and arbitrary rules as the plural for octopus actually just follows the regular English rule of adding the suffix -es to words ending in the letter s.
Despite octopodes and octopi not being recognized by most dictionaries as the plural of octopus, the graph below shows their appearances in written English since 1990 to be sizeable, especially the word octopi.
Here are some examples to illustrate the difference between "octopus" and "octopuses":
These examples show how "octopus" refers to a single animal, while "octopuses" refers to more than one animal.
The graph shows the occurances of the plural of octopus in written English since 1800 using Google's Ngram Viewer.
Just like moose, octopuses are actually very solitary creatures and you'll rarely find multiple octopuses together.