Private Security Authority, the state regulator for the security industry in the Republic of Ireland

Patient Safety Authority, a Pennsylvania state agency and Patient safety organization

Philmont Staff Association, the official organization of current and former staff members at Philmont Scout Ranch

Public Schools Association, an association of seven independent boys schools in Perth, Western Australia

Pushdown Stack Automaton

Prostate specific antigen, a substance that can be detected in the blood of men and which helps to determine if there may be a prostate cancer

Pacific Southwest Airlines, a former United States airline that flew passenger services in some Western states during the 1970s and early 1980s

PSA Peugeot Citroën, a French company which manufactures Peugeot and Citroën cars

Public service announcement, a non-commercial advertisement, broadcast for the public good

Property Services Agency, a former agency of the UK government concerned with buildings and estate management

PSA International, a port operator based in Singapore and an abbreviation for the now defunct Port of Singapore Authority

"PSA", the planned title of the song and single "Bad Day" by R.E.M.

Pressure sensitive adhesive, adhesive that is activated by pressure

PSA Airlines, a subsidiary of US Airways Group

Persistent sexual arousal syndrome, a spontaneous and persistent genital arousal

The Philippine Support Association, a support and awareness group for Oikocredit Philippines

Probabilistic safety assessment or Probabilistic risk assessment

Premier Soccer Alliance, the original name of the World Indoor Soccer League

Pressure Swing Adsorption, a special method for purifying gases

Professional Squash Association, the governing body for the men's professional squash circuit

Pharmaceutical Society of Australia, a professional organisation of Australian pharmacists

Profit Sharing Agreement, a financial arrangement between a company and a government for the company to extract oil or other resources and provide a portion of the profits from such extraction to the government

Pi Sigma Alpha

Product and Service Assembly, TMF industry model for CAD/CAM-derived approach to telecoms service creation

Professional Services Automation, refers to a suite of software enabling service organizations to manage people and skilled resources

Production sharing agreement, an agreement used to determine a company's share of natural resources extracted from a country

Prefixed Save Area, a common area of virtual storage from address zero through 8191 in every address space

PSA prepayment model, a prepayment model developed by the Public Securities Association

New Zealand Public Service Association, a large union for workers in the public sector of New Zealand

Polar surface area, the surface sum over of polar atoms, e.g. oxygen, nitrogen, etc

Public Securities Association, the former name of the Bond Market Association

Public Services Association, a trade union in Trinidad and Tobago

Philosophy of Science Association, an academic organization which promotes further studies and free discussion from diverse standpoints in the field of philosophy of science

Poultry Science Association, a poultry science association based in the United States

Polish Society of Actuaries, the professional association in Poland

Pacific Sociological Association, the professional association of sociologists in the Pacific Region of North America

Public Servants Association of South Africa, a trade union in South Africa

Political Studies Association, an academic association in the UK

Parramatta Salvation Army, A Salvation Army Corps in the Western Suburbs of Sydney, Australia

Galileo Galilei Airport, near Pisa, Italy with IATA code PSA.