Susan B. Anthony (born Susan Anthony; February 15, 1820 March 13, 1906) was an American social reformer and women's rights activist who played a pivotal role in the women's suffrage movement. Born into a Quaker family committed to social equality, she collected anti-slavery petitions at the age of 17. In 1856, she became the New York state agent for the American Anti-Slavery Society.

In 1851, she met Elizabeth Cady Stanton, who became her lifelong friend and co-worker in social reform activities, primarily in the field of women's rights. In 1852, they founded the New York Women's State Temperance Society after Anthony was prevented from speaking at a temperance conference because she was female. In 1863, they founded the Women's Loyal National League, which conducted the largest petition drive in United States history up to that time, collecting nearly 400,000 signatures in support of the abolition of slavery. In 1866, they initiated the American Equal Rights Association, which campaigned for equal rights for both women and African Americans. In 1868, they began publishing a women's rights newspaper called The Revolution. In 1869, they founded the National Woman Suffrage Association as part of a split in the women's movement. In 1890, the split was formally healed when their organization merged with the rival American Woman Suffrage Association to form the National American Woman Suffrage Association, with Anthony as its key force. In 1876, Anthony and Stanton began working with Matilda Joslyn Gage on what eventually grew into the six-volume History of Woman Suffrage. The interests of Anthony and Stanton diverged somewhat in later years, but the two remained close friends.

In 1872, Anthony was arrested in her hometown of Rochester, New York for voting in violation of laws that allowed only men to vote. She was convicted in a widely publicized trial. Although she refused to pay the fine, the authorities declined to take further action. In 1878, Anthony and Stanton arranged for Congress to be presented with an amendment giving women the right to vote. Introduced by Sen. Aaron A. Sargent (R-CA), it later became known colloquially as the Susan B. Anthony Amendment. It was eventually ratified as the Nineteenth Amendment to the U.S. Constitution in 1920.

Anthony traveled extensively in support of women's suffrage, giving as many as 75 to 100 speeches per year and working on many state campaigns. She worked internationally for women's rights, playing a key role in creating the International Council of Women, which is still active. She also helped to bring about the World's Congress of Representative Women at the World's Columbian Exposition in Chicago in 1893.

When she first began campaigning for women's rights, Anthony was harshly ridiculed and accused of trying to destroy the institution of marriage. Public perception of her changed radically during her lifetime, however. Her 80th birthday was celebrated in the White House at the invitation of President William McKinley. She became the first female citizen to be depicted on U.S. coinage when her portrait appeared on the 1979 dollar coin.

Women's suffrage is the right of women to vote in elections. Beginning in the mid-19th century, aside from the work being done by women for broad-based economic and political equality and for social reforms, women sought to change voting laws to allow them to vote. National and international organizations formed to coordinate efforts towards that objective, especially the International Woman Suffrage Alliance (founded in 1904 in Berlin, Germany), as well as for equal civil rights for women.Many instances occurred in recent centuries where women were selectively given, then stripped of, the right to vote. The first place in the world to award and maintain women's suffrage was New Jersey in 1776 (though in 1807 this was reverted so that only white men could vote).The first province to continuously allow women to vote was Pitcairn Islands in 1838, and the first sovereign nation was Norway in 1913, as the Kingdom of Hawai'i, which originally had universal suffrage in 1840, rescinded this in 1852 and was subsequently annexed by the United States in 1898. In the years after 1869, a number of provinces held by the British and Russian empires conferred women's suffrage, and some of these became sovereign nations at a later point, like New Zealand, Australia, and Finland. Women who owned property gained the right to vote in the Isle of Man in 1881, and in 1893, women in the then self-governing British colony of New Zealand were granted the right to vote. In Australia, non-Aboriginal women progressively gained the right to vote between 1894 and 1911 (federally in 1902). Prior to independence, in the Russian Grand Duchy of Finland, women were the first in the world to gain racially-equal suffrage, with both the right to vote and to stand as candidates in 1906. Most major Western powers extended voting rights to women in the interwar period, including Canada (1917), Britain and Germany (1918), Austria, the Netherlands (1919) and the United States (1920). Notable exceptions in Europe were France, where women could not vote until 1944, Greece (equal voting rights for women did not exist there until 1952, although, since 1930, literate women were able to vote in local elections), and Switzerland (where, since 1971, women could vote at the federal level, and between 1959 and 1990, women got the right to vote at the local canton level). The last European jurisdictions to give women the right to vote were Liechtenstein in 1984 and the Swiss canton of Appenzell Innerrhoden at local level in 1990. Since Saudi Arabia granted voting rights to women (2015), women can vote in every country that has elections.Leslie Hume argues that the First World War changed the popular mood:

The women's contribution to the war effort challenged the notion of women's physical and mental inferiority and made it more difficult to maintain that women were, both by constitution and temperament, unfit to vote. If women could work in munitions factories, it seemed both ungrateful and illogical to deny them a place in the voting booth. But the vote was much more than simply a reward for war work; the point was that women's participation in the war helped to dispel the fears that surrounded women's entry into the public arena.

Pre-WWI opponents of women's suffrage such as the UK Women's National Anti-Suffrage League cited women's relative inexperience in military affairs, women were the majority of the population, is the reason why women should vote in local elections but it would be dangerous to allow them to vote in national elections.Extended political campaigns by women and their supporters were necessary to gain legislation or constitutional amendments for women's suffrage. In many countries, limited suffrage for women was granted before universal suffrage for men; for instance, literate women or property owners were granted suffrage before all men received it. The United Nations encouraged women's suffrage in the years following World War II, and the Convention on the Elimination of All Forms of Discrimination Against Women (1979) identifies it as a basic right with 189 countries currently being parties to this convention.