The Clansman: A Historical Romance of the Ku Klux Klan is a novel published in 1905, the second work in the Ku Klux Klan trilogy by Thomas Dixon Jr. (the others are The Leopard's Spots and The Traitor). Chronicling the American Civil War and Reconstruction era from a pro-Confederate perspective, it presents the Ku Klux Klan heroically. The novel was adapted first by the author as a highly successful play entitled The Clansman (1905), and a decade later by D. W. Griffith in the 1915 movie The Birth of a Nation.

Dixon's novel portrays free blacks engaged in massive violent crimes against whites. He later claimed that 18,000,000 Southerners supported his beliefs. Dixon portrays the Radical Republican speaker of the house, Austin Stoneman (based on Thaddeus Stevens, from Pennsylvania), as a rapacious, vindictive, race traitor, mad with power and eaten up with hate. His goal is to punish the Southern whites for their revolution against an "oppressive" government (the Union) by turning the former slaves against the white Southerners and using the iron fist of the Union occupation troops to make them the new masters. In Dixon's characterization, the Klan's job is to protect white Southerners from the carpetbaggers and their allies, black and white.

The novel and its stage and film adaptations were highly controversial in their time, and continue to receive criticism for their espousal of racist and Neo-Confederate sentiments. In addition to concerns that The Clansman would stir up political and racial tensions in the South, Dixon's portrayal of the Klan as chivalrous freedom fighters was ridiculed as absurd.

In The Clansman, Reconstruction was an attempt by Augustus Stoneman, a thinly veiled reference to Representative Thaddeus Stevens of Pennsylvania, to ensure that the Republican Party would stay in power by securing the Southern black vote. Stoneman's hatred for President Johnson stems from Johnson's refusal to disenfranchise Southern whites. His anger towards former slaveholders is intensified after the assassination of Abraham Lincoln, when he vows revenge on the South. His programs strip away the land owned by whites, giving it to former slaves. (See Forty acres and a mule.) Men claiming to represent the government confiscate the material wealth of the South, destroying plantation-owning families. Finally, the former slaves are taught that they are superior to their former owners and should rise up against them. These injustices are the impetuses for the creation of the Klan.

Similar to his statements about The Leopard's Spots, Dixon insists in a "To the reader" prologue that the novel is historical:

I have sought to preserve in this romance both the letter and the spirit of this remarkable period. The men who enact the drama of fierce revenge into which I have woven a double love-story are historical figures. I have merely changed their names without taking a liberty with any essential historic fact.

The publication of The Clansman caused significant uproar not only in the North, but throughout the South. Thomas Dixon was denounced for renewing old conflicts and glorifying what many thought was an unfortunate part of American history.^{[citation needed]}

When offered membership in the KKK, Dixon reportedly turned it down because, he claimed, he did not agree with the Klan's methods. The Klokard of the Klan, Oscar Haywood, at one point challenged Dixon to a debate over the nature of the Ku Klux Klan.