The Labour leader gave a speech from a bandstand at the event in Derby Park, Bootle, on Saturday.
He described the danger of the far right and “their simplistic answers which can only breed hatred and division”.
Mr Corbyn compared the “propaganda” being put out by the far right during the European election campaign to the rise of the Nazis in Europe in the 1930s.
He said: “I read the propaganda being put out by the far right in this European election, where they’re blaming Muslims for all the ills of our society.
“Change that language to the language used in Germany in the 1920s and 1930s, where they tried to blame Jewish people for all the ills of society. You begin to see where this leads to.
“We have to come together today, not just to oppose the far right but also to analyse what’s happened and above all how we fix it and how we go forward.”
The crowd cheered as Mr Corbyn called for them to come together, defeat the far right and elect Labour politicians.
He said: “We have to stand together for the kind of world and the kind of society that we want to live in.”
He told the crowd: “If we don’t do something about it, that danger rises again.”
Mr Corbyn hit out at the Conservatives and Liberal Democrats for creating inequality in society, and he criticised the “mainstream media” for “trying to divide us, trying to destroy us, trying to weaken us”.
He said: “If we are to live in a world of peace, live in a world that can survive, deal with the great challenges of the world, you only do it by coming together, you only do it by pooling our minds, our brains, our energy, our imagination and our resources.
“If instead we allow the far right in Europe to mount once again the spectre, the scourge, the hatred of antisemitism in Poland, in Austria, in Germany, in Hungary, if we allow them to mount the spectre of Islamophobia in France, in the Netherlands or in this country, then we are weakening.”
About 500 supporters gathered from midday for the rally, which also featured speeches from local campaigners. The crowd booed when Mr Robinson’s name was mentioned and cheered when one speaker said June would be the “end of May” – in reference to prime minister Theresa May standing down.
Speakers urged the crowd to vote in Thursday’s elections to prevent a low turnout benefiting far-right candidates.
Bootle MP Peter Dowd said: “Bootle wants to send the message to these fascists and it’s quite simply, ‘Get lost’. Jeremy will be the next Labour prime minister and we are well on the way to that.”