A virucide (alternatively spelled viricide) is any physical or chemical agent that deactivates or destroys viruses. The substances are not only virucidal but can be also bactericidal, fungicidal, sporicidal or tuberculocidal.

Virucides are to be used outside the human body, and as such fall into the category of disinfectants (applied not to the human body) and antiseptics (applied to the surface of skin) for those safe enough. Overall, the notion of virucide differs from an antiviral drug such as Aciclovir, which inhibits the proliferation of the virus inside the body.

CDC's Disinfection and Sterilization list of Chemical Disinfectants mentions and discusses substances such as: alcohol, chlorine and chlorine compounds, formaldehyde, glutaraldehyde, hydrogen peroxide, iodophors, ortho-phthalaldehyde (OPA), peracetic acid, peracetic acid and hydrogen peroxide, phenolics, quaternary ammonium compounds, with different, but usually potent microbicidal activity. Other inactivating agents such as UV light, metals, and ozone exist.

According to the Centers for Disease Control and Prevention (CDC), a virucide is "An agent that kills viruses to make them noninfective."

According to a definition by Robert Koch Institute Germany and further institutions, virucide means effective against enveloped and non-enveloped viruses.

Due to the complexity of the subject, in Germany, Robert-Koch-Institute introduced sub-definitions such as "limited virucidal" or "limited virucidal plus" (translated from German) to differentiate its meaning further.

Note that the meaning of virus inactivation or viral clearance is specific for the medical process industry, i.e., to remove HIV from blood.

Different substances have interactions between microbicides and viruses such as: