Annihilator may refer to:

• Annihilator guitar, a custom-built guitar
• Annihilator (ring theory), a mathematical concept
• The annihilator of a vector subspace
• Annihilator method, a type of differential operator, used in a particular method for solving differential equations
• Annihilator (band), a Canadian thrash metal band
• Annihilator (truck), a monster truck
• Annihilator (Justice League), a fictional automaton used in the series, Justice League Unlimited.