A statue of British women's rights leader Millicent Fawcett was unveiled in Parliament Square on Tuesday, the first monument to a woman to be erected on the historic site.

Fawcett, one of the leading campaigners for equal rights, will be commemorated in a ceremony to mark 100 years since women won the vote.

Fawcett founded the National Union of Women's Suffrage and in 1866 at the age of 19 collected signatures for the first petition demanding the right for women to vote to be handed into parliament.

The bronze casting by artist Gillian Wearing shows Fawcett holding a banner reading "courage calls to courage everywhere."

It will stand alongside 11 statues of mostly British statesman such as wartime prime minister Winston Churchill.

The square, which backs onto Britain's parliament and is often a centre of political protest, also includes monuments to Indian independence leader Mahatma Gandhi and South African President and anti-apartheid leader Nelson Mandela.

"The struggle to achieve votes for women was long and arduous and Dame Millicent was there from the beginning," British Prime Minister Theresa May said at the unveiling.

"For decade after decade, in the face of often fierce opposition, she travelled the country and the world, campaigning not just for the vote but on a whole range of issues."