Obstruction of justice, in United States jurisdictions, is an act that involves unduly influencing, impeding, or otherwise interfering with the justice system, especially the legal and procedural tasks of prosecutors, investigators, or other government officials. Common law jurisdictions other than the United States tend to use the wider offense of perverting the course of justice.

Obstruction is a broad crime that may include acts such as perjury, making false statements to officials, witness tampering, jury tampering, destruction of evidence, and many others. Obstruction also applies to overt coercion of court or government officials via the means of threats or actual physical harm, and also applying to deliberate sedition against a court official to undermine the appearance of legitimate authority.