Psi, PSI or Ψ may refer to: Alphabetic letters Psi (Greek) (Ψ, ψ), the 23rd letter of the Greek alphabet Psi (Cyrillic) (Ѱ, ѱ), letter of the early Cyrillic alphabet, adopted from Greek Arts and entertainment "Psi" as an abbreviation for psionics Comics Psi (comics), DC Comics character Psi Division, division in the Judge Dredd and 2000 AD series of comics Psi-Force, comic series Psi-Hawk, comic character Psi Lords, comic series Music PSI (album), album by Pitchshifter (2002) Psi Com, 1980s rock band Psi Power, song by rock group Hawkwind (1978) PSI Records, music record label Ψ CMX DVD, Finnish language video album by the band CMX Pitch Shifter Industries, acronym used by the British band Pitchshifter Logo used by the band Twenty One Pilots during their Scaled and Icy (2021) album era Other uses in arts and entertainment Psi (TV series), Brazil Psi Corps, in the Babylon 5 fictional universe Psi Factor: Chronicles of the Paranormal, Canadian television series Psi-Ops: The Mindgate Conspiracy, 2004 video game Organizations Government and politics Italian Socialist Party (Partito Socialista Italiano), socialist and later social-democratic political party in Italy Italian Socialist Party (2007), social-democratic political party in Italy Indonesian Solidarity Party (Partai Solidaritas Indonesia) Indonesian Socialist Party (Partai Sosialis Indonesia) Proliferation Security Initiative, against weapons technology transfer Public Sector Information, as in: The 2003 EU Directive on the re-use of public sector information The UK Office of Public Sector Information (OPSI), formerly HMSO United States Senate Homeland Security Permanent Subcommittee on Investigations Other organizations Paul Scherrer Institute, research institute in Villigen, Switzerland Pechersk School International, Kyiv, Ukraine Physics Society of Iran Planetary Science Institute, Tucson, Arizona, US Poetry Slam, Inc., promoting poetry Policy Studies Institute, UK research organization Population Services International, global health organization Professional Skills Institute, technical school in Maumee, Ohio, US Prudential Securities Incorporated, financial services company PSI Seminars, on awareness training Public Services International, trades unions federation Statisticians in the Pharmaceutical Industry Parapsychology Psi (parapsychology), psychic or paranormal phenomena Psi hit, parapsychological experimentation term Paranormal Site Investigators, in the UK Science, technology, and mathematics Biology and medicine PSI (prion), infectious protein in yeast Pandemic severity index, former US CDC influenza scale Photosystem I, protein complex involved in photosynthesis Pneumonia severity index Protein Structure Initiative, of the U.S. NIGMS Computing Psi (instant messaging client), XMPP client program Potentially Shippable Increment, in the Scrum software development methodology Program-specific information, part of the MPEG