Sir is a respectful form of address for a man, and a formal title used in the United Kingdom for knights and baronets.

Sir, SIR or SiR may also refer to:

Places Iran Sir, Iran, Fars Province Sir, Razavi Khorasan Sir, West Azerbaijan

Palestine Sir, Jenin Sir, Tulkarm

Elsewhere Sir Creek, on the India–Pakistan border Sır Dam, Turkey Saskatchewan International Raceway, Canada

People Sir (singer), American singer, songwriter, record producer Jaroslav Šír (born 1923), Czechoslovak former skier József Sir (1912–1996), Hungarian sprinter Sedat Sir (born 1975), Turkish-Australian former Australian Rules footballer

Entertainment Characters Sir (A Series of Unfortunate Events), a fictional character in A Series of Unfortunate Events Sir, or Mark Thackeray, the title character of the 1967 film To Sir, with Love

Film Sir (1993 film), an Indian Hindi-language crime drama film Sir (2018 film), an Indian Hindi-language romantic drama film Sir (2023 film), an Indian Telugu-language version of Vaathi Sir (2024 film), an Indian Tamil-language action drama film Sir (2025 film), an Indian Odia-language drama film

Music Sir (album), by Fischerspooner, 2018 "Sir", a song by Nicki Minaj from Queen, 2018

Organizations Security Industry Registry, a corporate service provided by the New South Wales Police Force Sigma Iota Rho, a collegiate honour society for international studies Singapore Infantry Regiment, the main formation of the Singapore Army Society of Interventional Radiology, an American organization of health professionals Sons In Retirement, a fraternal organization of retired men

Science and technology SIR model, a compartmental model of the progress of an epidemic Secondary image registration, a type of passive autofocus in cameras Sequential Importance Resampling, a particle filtering algorithm Serial Infrared, the physical layer of the IrDA standard for data transmission Short interest ratio, a metric signalling prevailing investors' sentiment Signal-to-interference ratio, the ratio of useful signal versus co-channel interference received Silent information regulator protein involved in regulating gene expression Supplemental inflatable restraint or airbag, a vehicle safety device

Transportation

Siantar railway station, Pematang Siantar, Indonesia South Indian Railway, an early Indian railway company Staten Island Railway, rapid transit line in the borough of Staten Island, New York, United States Surrey Iron Railway, a horse-drawn plateway that linked the former Surrey towns of Wandsworth and Croydon Sion Airport, the airport in Sion, Switzerland whose IATA code is SIR

Other uses Sirene (Sir in Serbian), a type of cheese Statutory Invention Registration, a publication of an invention by the United States Patent and Trademark Office Special Intensive Revision, an exercise undertaken by the Election Commission of India to prepare the voters list

See also Siir (disambiguation)