ONT could mean:
- LA/Ontario International Airport (IATA code ONT), in Ontario, California, United States
- Ontario, although ON is the proper postal abbreviation
- Optical Network Terminal, an interface between a telephone company's fiber optic network and premises wiring
- Ontario Northland Railway, a Canadian railroad
- Ordo Novi Templi, Order of the New Templars, an occult anti-semitic society founded 1907 by Lanz von Liebenfels
- Ontario Network Television, the main predecessor of the now-defunct Baton Broadcast System (Canada)
- Obshchenatsional'noe Televidenie, a Belarusian national television station
- ortho-nitrotoluene, a type of mononitrotoluene, a nitro compound derivate of toluene
- Organización Nacional de Transplantes (Spanish Transplant Organization), which manages human organ and tissue transplants in Spain