Illinois v. Allen, 397 U.S. 337 (1970), was a decision by the Supreme Court of the United States regarding the removal of an unruly criminal defendant during his trial.

During jury selection, Allen began arguing with the judge using profane language and behaving in a highly disrespectful manner.

Later, having assured the judge that he would reform his conduct, Allen was allowed to return to the courtroom while his attorneys presented the defense's case.

Later, the Court of Appeals reversed, saying that the right to be present at one's own trial is so absolute that no defendant, regardless of his conduct, can be held to have forfeited it so long as he insisted on it, as Allen had done.

During the Waukesha Christmas parade attack trial, Judge Jennifer Dorow repeatedly cited the Supreme Court's decision in Allen as her authority to remove the defendant, Darrell Brooks, from her courtroom, after she had warned him that this could happen.