'''P4''' may refer to: {{TOC right}}
==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'', a 2019 album by American progressive metal band Periphery * ''PartyNextDoor 4'', a 2024 album by Canadian singer PartyNextDoor * ''Psychonaut 4'', a Georgian black metal band
==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 (P<sub>4</sub>), an allotrope of phosphorus * Group p4, the plane symmetry group wallpaper group ''p''4 * 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 * P4, three-dimensional space group number 75 * P{{overline|4}}, three-dimensional space group number 81
==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 {{chem2|PO4(3-)}}<!--PO4 redirects to Phosphate; easily mistaken for P04, which redirects to here--> * Play (telecommunications) P4, a Polish cellular telecommunications provider
{{Letter-number combination disambiguation}}