PID
PID or Pid may refer to:
Medicine
- Pelvic inflammatory disease or pelvic inflammatory disorder, an infection of the upper part of the female reproductive system
 - Primary immune deficiency, disorders in which part of the body's immune system is missing or does not function properly
 - Prolapsed intervertebral disc, commonly called a herniated disc
 
Science, technology and engineering
- BBC Programme Identifier, a unique identifier for a BBC television or radio programme brand, a season or series, or an individual episode
 - OBD-II PIDs (on-board diagnostics parameter IDs), requests for data through an OBD connector in automotive repair
 - Packet Identifier, a field in a MPEG transport stream packet
 - Partial information decomposition, an extension of information theory
 - Passive infrared detector, a passive infrared sensor
 - Payload Interface Document (used on space engineering program for example)
 - Persistent identifier, a long-lasting reference to a document, file, web page, or other object
 - Phosphotyrosine-interacting domain, also known as phosphotyrosine-binding domain, a protein domain which bind to phosphotyrosine
 - Photoionization detector, measures volatile organic compounds and other gases
 - Physical Interface Device, a class of a USB device
 - PID controller (proportional-integral-derivative controller), a control concept used in automation
 - Piping and instrumentation diagram (P&ID), a diagram in the process industry which shows the piping of the process flow etc.
 - Principal ideal domain, an algebraic structure
 - Process identifier, a number used by many operating systems to identify a process
 
Organisations
- Police Intelligence Department, a staff department of the Singapore Police Force
 - Political Intelligence Department (disambiguation), multiple organisations
 - Politieke Inlichtingen Dienst (Political Intelligence Department), was the main security agency for the Dutch East Indies
 - Prague Integrated Transport (Pražská integrovaná doprava – PID in Czech), an integrated public transport system in Prague
 - Press Information Department, government department of Bangladesh
 
Other uses
- Pathways into Darkness, a 1993 video game by Bungie
 - "Paul is dead", a 1960s urban legend that Paul McCartney was dead
 - Pid (video game), a 2012 video game by Might and Delight
 - Project Initiation Documentation, in project management
 - Party identification, the political party with which an individual identifies
 - Everett Pid Purdy (1904–1951), American athlete who played in both Major League Baseball and the National Football League
 - P.I.D., Christian hip-hop group