PDE may refer to:

• Partial differential equation, differential equation involving partial derivatives (of a function of multiple variables)

• Phosphodiesterase, enzyme important in intracellular communication
• Pug dog encephalitis

• The European Democratic Party (esp. in Spanish, French or Italian languages)
• The Pennsylvania Department of Education

• Program development environment
• Pulse detonation engine, proposed substitute to the traditional jet engine

• Principle of double effect

• Punta del Este

• Polydichloric euthimal, fictional substance
• Pde (or Pde.), "Parade" (when serving as part of the proper name of a street or other way)
• Present Day English