P4 may refer to:

Computing

• Intel Pentium 4, a processor series shipped from 2000 to 2008
  • The P4 power connector, introduced in the ATX12V 1.0 standard to power these and later CPUs
• The i486DX (P4) model of the Intel 80486 microprocessor, introduced in 1989
• P4 (programming language), for controlling network data forwarding
• P4, the Perforce software command line client

Media

• P4 Radio Hele Norge (PFI), a Norwegian radio company
  • Kanal 24 (Kanal 4), which acquired the Norwegian P4 channel from PFI
• Sveriges Radio P4, a Swedish radio channel
• Persona 4, a 2008 video game
• Periphery IV: Hail Stan, 2019 album by American progressive metal band Periphery

Military

• Skaraborg Regiment (armoured), a Swedish army unit, designated P 4
• Peugeot P4, a French military vehicle

Science

• P4 laboratory, a biosafety level 4 facility
• Tetraphosphorus (P₄), an allotrope of phosphorus
• Group p4, the plane symmetry group wallpaper group p4
• Progesterone (Pregn-4-ene-3,20-dione), a steroid hormone
• Kerberos, the fourth moon of Pluto
• Perfect fourth, a musical interval
• Enterobacteria phage P4
• P4, an EEG electrode site according to the 10-20 system
• P4 cell, a stage in the Caenorhabditis elegans embryonic development
• P4-metric, in statistics, a performance metric

Roads

• P4 road (Latvia)
• P04 road (Ukraine)

Other uses

• Papyrus 4, a New Testament manuscript
• Trans-Pacific Strategic Economic Partnership, or P4, a free trade agreement between Brunei, Chile, New Zealand, and Singapore
• Prussian P 4, a German steam locomotive
• Protofour, or P4, a set of standards for model railways

See also

• 4P (disambiguation)
• Phosphate, molecular formula PO₄^3−.
• Play (telecommunications) P4, a Polish cellular telecommunications provider