William Henry Seward (May 16, 1801 October 10, 1872) was an American politician who served as United States Secretary of State from 1861 to 1869, and earlier served as governor of New York and as a United States Senator. A determined opponent of the spread of slavery in the years leading up to the American Civil War, he was a prominent figure in the Republican Party in its formative years, and was praised for his work on behalf of the Union as Secretary of State during the Civil War. He also negotiated the treaty for the United States to purchase the Alaskan Territory.

Seward was born in 1801 in the village of Florida, in Orange County, New York, where his father was a farmer and owned slaves. He was educated as a lawyer and moved to the Central New York town of Auburn. Seward was elected to the New York State Senate in 1830 as an Anti-Mason. Four years later, he became the gubernatorial nominee of the Whig Party. Though he was not successful in that race, Seward was elected governor in 1838 and won a second two-year term in 1840. During this period, he signed several laws that advanced the rights of and opportunities for black residents, as well as guaranteeing jury trials for fugitive slaves in the state. The legislation protected abolitionists, and he used his position to intervene in cases of freed black people who were enslaved in the South.

After many years of practicing law in Auburn, he was elected by the state legislature to the U.S. Senate in 1849. Seward's strong stances and provocative words against slavery brought him hatred in the South. He was re-elected to the Senate in 1855, and soon joined the nascent Republican Party, becoming one of its leading figures. As the 1860 presidential election approached, he was regarded as the leading candidate for the Republican nomination. Several factors, including attitudes to his vocal opposition to slavery, his support for immigrants and Catholics, and his association with editor and political boss Thurlow Weed, worked against him, and Abraham Lincoln secured the presidential nomination. Although devastated by his loss, he campaigned for Lincoln, who appointed him Secretary of State after winning the election.

Seward did his best to stop the southern states from seceding; once that failed, he devoted himself wholeheartedly to the Union cause. His firm stance against foreign intervention in the Civil War helped deter the United Kingdom and France from recognizing the independence of the Confederate States. He was one of the targets of the 1865 assassination plot that killed Lincoln and was seriously wounded by conspirator Lewis Powell. Seward remained in his post through the presidency of Andrew Johnson, during which he negotiated the Alaska Purchase in 1867 and supported Johnson during his impeachment. His contemporary Carl Schurz described Seward as "one of those spirits who sometimes will go ahead of public opinion instead of tamely following its footprints".

The United States secretary of state is an officer of the United States who implements foreign policy for the U.S. government as the head of the U.S. Department of State. The office holder is one of the highest ranking members of the president's Cabinet, and ranks the first in the U.S. presidential line of succession among Cabinet secretaries.

Created in 1789 with Thomas Jefferson as its first office holder, the secretary of state represents the United States to foreign countries, and is therefore considered analogous to a foreign minister in other countries. The secretary of state is nominated by the president of the United States and, following a confirmation hearing before the Senate Committee on Foreign Relations, is confirmed by the United States Senate. The secretary of state, along with the secretary of the treasury, secretary of defense, and attorney general, are generally regarded as the four most crucial Cabinet members because of the importance of their respective departments.Secretary of State is a Level I position in the Executive Schedule and thus earns the salary prescribed for that level (US$221,400, as of January 2021). The current secretary of state is Antony Blinken, who was confirmed on January 26, 2021 by the Senate by a vote of 78–22.