SEF may refer to:
- Supplementary eye fields, areas in the primate brain that are involved in planning and control of saccadic eye movements
- Spectral edge frequency, a measure used in signal processing
- Sankara Eye Foundation, a non-profit that works for eradicating curable blindness in India
- Sinfonia Educational Foundation, the philanthropic arm of the Phi Mu Alpha Sinfonia Music Fraternity
- Straits Exchange Foundation, a semi-official organization of Taiwan that deals with the business matters with China
- Swedish Electricians' Union, a trade union in Sweden
- Swedish Esperanto Federation, an organization of Esperanto speakers in Sweden
- South Eastern Freeway, a Freeway in Australia
- Stadio Erinis & Filias, the Greek name for Peace and Friendship Stadium, an indoor sports arena in Athens
- Self-Extinguishing Fabric, part of a brand name for modacrylic fiber
- SharePoint & Exchange Forum, an annual 2-day conference in Stockholm, Sweden, hosted by HumanData
- Small Enterprise Foundation, a microfinance institution operating primarily in the Limpopo province of South Africa
- Sustainable Environment Fund act, created by the government of British Columbia, Canada in 1990
- Science Education Foundation
- Search Engine Friendly, a way to format URLs for search engine optimization
- Social Engine Forum, an unofficial virtual collaborative community for SocialEngine software related contents
- Sicher/Einzelfeuer/Feuerstoß, a trigger grouping used on Heckler & Koch guns such as the MP5
- Short Edge Feed, a direction to feed paper to printers. Also used in combination with the paper size, e.g. A4 SEF
- Swap Execution Facility, A platform for regulated trading and clearing of swaps to be required in the United States by the Dodd-Frank bill
- Serviço de Estrangeiros e Fronteiras, Portuguese Border and Alien Service