Henry Mayers Hyndman (/ˈhaɪndmən/; 7 March 1842 – 20 November 1921) was a British writer and politician.

Originally a conservative, he was converted to socialism by Karl Marx's Communist Manifesto and launched Britain's first left-wing political party, the Democratic Federation, later known as the Social Democratic Federation, in 1881.

Although this body attracted radicals such as William Morris and George Lansbury, Hyndman was generally disliked as an authoritarian who could not unite his party. Nonetheless, Hyndman was the first author to popularize Marx's works in English.