The nineteenth century writer won September's vote with a clear margin, pushing Albert Einstein, who had led for most of the month, into second place.

The top 10 included philosophers Immanuel Kant and Rene Descartes as well as twentieth century scientist Stephen Hawking.

The vote was the ninth of BBC News Online's monthly Your Millennium series. In October you can vote for the greatest explorer of the last thousand years.

To inspire you, two record-breaking British explorers, Brian Jones and David Hempleman-Adams, have contributed their personal top-10 lists.

Karl Marx is probably the most influential socialist thinker to emerge in the nineteenth century and one of the founders of communism.

Although dictatorships throughout the twentieth century have distorted his original ideas, his work as a philosopher, social scientist, historian and a revolutionary is respected by academics today.

Karl Heinrich Marx (1818-1883) was born into a middle-class family in Germany, but he became a revolutionary in Paris, Brussels and London.

He met the like-minded Friedrich Engels (1820-1895) in France. Together they wrote The Communist Manifesto, which outlined the theory of the class struggle. Marx was exiled from Paris and Brussels for his revolutionary activities and settled in London where he lived until his death.

Amongst Marx's other influential works are the Economic and Philosophical Manuscripts, which remained unpublished until the 1930s, and the monumental work Das Kapital.

BBC News Online readers from across the world took part in the millennium poll.

Dag Thoresen from Norway, said: "Karl Marx has inspired thousands of liberation struggles. He was the father of modern political thinking."

And Jyotsna Kapur from the USA said: "Marx analysed best the working of capitalism. Given that that is the system that characterises the world at the end of the twentieth century his work is as relevant to understanding the world we live in as it was for understanding the nineteenth century."

Click here to see the full results of September's vote.