US president Donald Trump has announced he will posthumously pardon women’s rights campaigner Susan B. Anthony.

Anthony was arrested in 1872 for voting and Trump’s pardon marks the 100-year anniversary of the ratification of the 19th amendment which allowed women to vote.

“Later today, I will be signing a full and complete pardon for Susan B. Anthony. She was never pardoned. Did you know that? She was never pardoned," said Trump.

"She was never pardoned — for voting. She was guilty for voting. And we are going to be signing a full and complete pardon, and I think that's really fantastic.”

And noting that there are many women now sitting in Congress he added: “Women dominate the United States - I think we can say that very strongly.”

This comes as Trump is ramping up his campaigning targeted at women for the presidential election in November, as support for him among white suburban women is said to be decreasing.

In recent weeks his administration has launched a ‘Women for Trump’ bus tour and he has stepped up his messages surrounding law and order.

Anthony was arrested in her hometown of Rochester in New York and was convicted of voting in a much-publicised trial. But she refused to pay the $100 fine.

The 19th amendment, also known as the Susan B. Anthony amendment, states: "The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of sex".

Congress passed the amendment in 1919 but it wasn’t until a year later that it was ratified.

Anthony did not live to see it passed as she died in 1906.