A die-in, sometimes known as a lie-in, is a form of protest in which participants simulate being dead. Die-ins are actions that have been used by a variety of protest groups on topics such as animal rights, anti-war, against traffic violence, human rights, AIDS, gun control, racism, abortion, and environmental issues. Often, protestors occupy an area for a short time instead of being forced to leave by the police.

In the simplest form of a die-in, protesters simply lie down on the ground and pretend to be dead, sometimes covering themselves with signs or banners. The point of a die-in is to disrupt the flow of people on a street or sidewalk to grab the attention of passers-by.

In more complex forms, fake blood or blood-stained bandages are sometimes used, as well as simulated death throes and writhing from the protesters in an attempt to make the deaths appear more realistic. In other cases, protesters have surrounded the "bodies" in chalk outlines reminiscent of the troped outlines around murder victims. This has been done as an attempt to symbolize that the organization being protested against has "murdered" people. Sometimes, part of the protesting group makes speeches about what is being protested while the rest of the group lies on the ground.