Se may stand for:

• Selenium, a chemical element
• Se (kana) (せ and セ), a Japanese kana
• Se (unit of measurement) (畝), a Japanese unit of area
• Northern Sami language ISO 639-1 code
• Se (instrument) (瑟), a traditional Chinese musical instrument

Sé may refer to:

• sé, the word 'he', or the number six in the Irish language.
• Sé (district of São Paulo), a district of São Paulo, Brazil
• Sé, Hungary, a village in Hungary
• One of several parishes in Portugal:
  • Sé (Angra do Heroísmo), a parish in Angra do Heroísmo
  • Sé (Braga), a parish in Braga
  • Sé (Bragança), a parish in Bragança
  • Sé (Faro), a parish in Faro
  • Sé (Funchal), a parish in Funchal
  • Sé (Guarda), a parish in Guarda
  • Sé (Lamego), a parish in Lamego
  • Sé (Lisboa), a parish in Lisbon
  • Sé (Portalegre), a parish in Portalegre
  • Sé (Porto), a parish in Porto
• A parish in Macao, formerly a Portuguese overseas province
  • , a parish in Concelho de Macau, one of the two concelhos of Macao
• Sé, an album by Lúnasa

.se is the Internet country code top-level domain (ccTLD) for Sweden (Sverige). The top domain is operated by .SE (The Internet Infrastructure Foundation), but domains must be registered through one of the approved registrars. .SE is a foundation and is managed on the basis of its charter of foundation and its statutes. The Foundation is managed by a Board of Directors, whose decisions are executed by the executive management.