PY, Py, py or P-Y may stand for:

• Eugène Py, a French cinema pioneer of the Cinema of Argentina
• Jorge Py, a Brazilian footballer
• Olivier Py, a French stage director, actor and writer
• Delphine Py-Bilot, a French triathlete
• Piye, a Kushite king and founder of the Twenty-fifth dynasty of Egypt
• Pierre-Yves Gerbeau, French businessman

• Python (programming language), which uses the filename extension '.py'
• .py, the country code top level domain (ccTLD) for Paraguay
• py (unit), a Korean unit of floorspace area
• petayear, Py, 10¹⁵ year
• Py (cipher), a stream cipher designed by Eli Biham and Jennifer Seberry
• p-y method, for assessing the load-bearing abilities of deep foundations
• Permalloy, a nickel-iron magnetic alloy
• Pyridine, a common monodentate ligand in coordination chemistry, abbreviated as 'py'

• Py, Pyrénées-Orientales, a commune of the Pyrénées-Orientales département in southwestern France
• Pack year, a measure of cigarette smoking
• Paraguay, ISO 3166-1 country code
• Puducherry, formerly Pondicherry, a union territory of India
• Pinyin, a system of romanization (phonetic notation and transliteration to Roman script) for Mandarin Chinese
• Portsmouth yardstick, used as a rating system in yacht racing and dinghy racing
• Surinam Airways (IATA airline designator PY)
• A US Navy hull classification symbol: Patrol yacht (PY)