GPI may refer to:

• Alpha GPI, a Brazilian submachine gun.
• Greenfield Park International, a primary school in Greenfield Park, Quebec, Canada.
• Gas Petroleum&Properties Investments, LLC. Limited Liability Company, Oil Trading and Investment Consulting, Premium Real Estate Brokers based in Dubai, United Arab Emirates.
• Gemini Planet Imager, an instrument being built to directly image extrasolar planets
• Gender Parity Index, a measure that reflects females’ level of access to education compared to that of males’ access.
• General paresis of the insane, a now-rare neuropsychiatric disorder affecting the brain and central nervous system
• General Purpose Interface, Standard contact closure format used in broadcast level post production equipment, allowing computer based editing equipment to synchronously "start" at the same time.
• General Purpose Input
• Genuine Progress Indicator, a concept economics that has been suggested as a replacement metric for gross domestic product
• Glacier Park International Airport, a public airport serving Flathead County, Montana
• Glass Packaging Institute, a trade association for the U.S. glass container industry
• Global Partnership Initiative, an initiative of the United Nations Human Settlement Programme (UN-HABITAT).
• Global Peace Index, an index for the relative position of nations’ and regions’ peacefulness
• Global Poverty Initiative, a student group at Massachusetts Institute of Technology focused on alleviating worldwide poverty that hosted the Inaugural Millennium Campus Network Conference in April 2008.
• Global Protection & Intelligence, Inc. Private Public Figure, Executive, Diplomatic protective service based in Los Angeles, California USA.
• Internal globus pallidus, a part of the basal ganglia.
• Glucose Phosphate Isomerase, an enzyme
• Glycophosphatidylinositol, a glycolipid that can be attached to the C-terminus of a protein during posttranslational modification
• Granite Peak Installation, a World War II U.S. biological weapons testing facility
• Greenman-Pedersen, Inc., an engineering firm headquartered in Babylon, New York.
• Grove Park Inn, a resort hotel in Asheville, North Carolina
• Gurley Precision Instruments, an ISO-9001 certified U.S. manufacturing company based in Troy, New York
• Glycoprotein inhibitors, a class of antiplatelet agent.

The medial globus pallidus (or internal, GPi) is one of the output nuclei of the basal ganglia (the other being the substantia nigra pars reticulata). The GABA-containing neurons send their axons to specific nuclei of the dorsal thalamus (VA and VL), to the centromedian complex and to the pedunculopontine complex.