Spillover may refer to:

• Adsorption spillover, a chemical phenomenon involving the movement of atoms adsorbed onto a metal surface
• Catalyst support#Spillover
• Behavioral spillover, the effect that one behavior has on other behaviors with a shared motive
• Hydrogen spillover
• Knowledge spillover, exchange of ideas among individuals
• Spillover (book), or Spillover: Animal Infections and the Next Human Pandemic, a 2012 book by David Quammen
• Spillover (economics), an economic event that occurs because of an event in a seemingly unrelated context
• Spillover (imaging), in e.g. tomography, an imaging effect that exaggerates small objects, because of limited resolution
• Spillover infection or pathogen spillover occurs when an infectious reservoir population affects a novel host
• Spillover-crossover model, in psychology distinguishes spillover from crossover as components of transfer of well-being