Here's one of the earliest examples, from 1894:
Nazi Germany used the motif often. Mein Kampf referred to Jews as octopuses, and this Nazi cartoon portrayed Churchill as a Jewish octopus:
Another from the cover of a German magazine:
The transition from octopus-as-Jew to octopus-as-Israel is keenly shown here in a 1952 Syrian book cover:
The Soviet Union also freely used the octopus as both symbolizing Zionism and Jews:
Nowadays, the octopus is used for "Zionists," although it is very clear that they mean Jews, both the modern antisemites:
And Arab antisemites:
The octopus motif shows that that there is no difference between anti-Zionism and antisemitism.
(h/t Tomer)