PSA, PsA, Psa, or psa may refer to:

• PSA Airlines, a subsidiary of US Airways, Inc.
• Pisa International Airport, Pisa, Italy, IATA code PSA
• Pacific Southwest Airlines, US, 1949 to 1988, ICAO code PSA

Pi Sigma Alpha (ΠΣΑ or PSA), the National Political Science Honor Society, is the only honor society for college and university students of political science in the United States. Its purpose is to recognize and promote high academic achievement in the field of political science. It is a member of the Association of College Honor Societies (ACHS) and adheres to all the standards set by ACHS for an upper-division, specialized honor society. Pi Sigma Alpha is not a social fraternity or club.

Piscis Austrinus (also known as Piscis Australis) is a constellation in the southern celestial hemisphere. The name is Latin for "the southern fish", in contrast with the larger constellation Pisces, which represents a pair of fishes. Prior to the 20th century, it was also known as Piscis Notius. Its only star brighter than 4th magnitude is Fomalhaut, which is a first-magnitude star and is the 18th brightest star in the night sky.

The Book of Psalms, Tehillim in Hebrew ( or   meaning "Praises"), commonly referred to simply as Psalms or "the Psalms", is the first book of the Ketuvim ("Writings"), the third section of the Hebrew Bible, and a book of the Christian Old Testament. The title is derived from the Greek translation, ψαλμοί psalmoi, meaning "instrumental music" and, by extension, "the words accompanying the music." The book is an anthology of individual , with 150 in the Jewish and Western Christian tradition and more in the Eastern Christian churches. Many of the psalms are linked to the name of King David, although his authorship is not accepted by modern Bible scholars.