Andrew Johnson (December 29, 1808 – July 31, 1875) was the 17th President of the United States (1865–1869). As Vice President of the United States in 1865, he succeeded Abraham Lincoln following the latter's assassination. Johnson then presided over the initial and contentious Reconstruction era of the United States following the American Civil War. Johnson's reconstruction policies failed to promote the rights of the Freedmen, and he came under vigorous political attack from Republicans, ending in his impeachment by the U.S. House of Representatives; he was acquitted by the U.S. Senate.

Johnson, born in poverty and of Scots-Irish descent, became a master tailor and was self-educated, married and had five children. He served as an alderman and as Mayor of Greeneville, Tennessee and then sat in both houses of the Tennessee legislature. He went on to spend five consecutive terms in the U.S. House of Representatives and two terms as Governor of Tennessee, all as a Democrat. His signature legislative endeavor in the state and federal arenas was passage of the Homestead Act.

When Tennessee seceded from the Union in 1861, Johnson was a Democratic U.S. Senator from Tennessee and was dedicated to a limited government. Also a Unionist, but pro-slavery, he was the only Southern senator not to resign his seat during the Civil War, became the most prominent War Democrat from the South and supported Lincoln's military policies. In 1862, Lincoln appointed Johnson military governor of occupied Tennessee, where he was effective in fighting and ending the rebellion; he implemented Reconstruction policies in the state and transitioned for a time to a pro-emancipation policy.

Johnson was nominated as the vice presidential candidate in 1864 on the National Union Party ticket. He and Lincoln were elected in 1864, inaugurated in early 1865 and a month later Johnson assumed the presidency upon Lincoln's assassination.

As president, he implemented his own form of Presidential Reconstruction – a series of proclamations directing the seceded states to hold conventions and elections to re-form their civil governments. These proclamations embodied Johnson's conciliatory policies towards the South, as well as his rush to reincorporate the former Confederate states into the union without due regard for freedmen's rights; these positions and his vetoes of civil rights bills embroiled him in a bitter dispute with Radical Republicans who demanded harsher measures. The Radicals were infuriated with Johnson's lenient policies. The Radicals in the House of Representatives impeached him in 1868 (a first for a U.S. president), charging him with violating the Tenure of Office Act, when he sought to remove his Secretary of War without Senate approval; nevertheless, his trial in the Senate ended in an acquittal by a single vote.

As a Jeffersonian and Jacksonian, Johnson refused to toe any party line throughout his political career – though he primarily ran as a Democrat, with the exception of his vice-presidency. While president he attempted to build a party of loyalists under the National Union label. His failure to make the National Union brand a genuine party made Johnson an independent during his presidency, though he was supported by Democrats and later rejoined the party briefly as a Democratic Senator from Tennessee in 1875 until his death that year. Johnson's administration has received very poor historical rankings amongst scholars, typically amongst the bottom