The official Ontario abbreviation is ON, the two-letter province code set by Canada Post. Write both letters as capitals, without a period, between the city and the postal code on an address. The traditional short form is Ont., with a period, which you may still see in older documents and some news writing.
Ontario is a Canadian province, not a state, but people in the United States often search for its "state abbreviation" when filling out a shipping form or a drop down list. The answer is the same: choose ON. Ontario is home to Toronto, Canada's largest city, and to Ottawa, the national capital.
Quick facts
Postal code
ONTraditional
Ont.ISO code
CA-ONPostal codes start with
K, L, M, N or PCapital
TorontoNot to be confused with
OH (Ohio), OR (Oregon), ONT (an airport in California)
Ontario abbreviation forms side by side
| Short form | Kind of code | Best fit |
|---|---|---|
| ON | Canada Post province code | Envelopes, packages, online forms |
| Ont. | Traditional abbreviation | Older records, some datelines and citations |
| CA-ON | International subdivision code | Databases and data files |
| Ontario | Full name | Sentences and most writing |
Canada's two-letter province codes work much like US state codes. You can see the whole country's set on our Canada abbreviation page.
Is there an ON state abbreviation?
Strictly, no, because Ontario is a province. But many US websites put Canadian provinces in the same menu as the fifty states, labeled "State/Province." In that list, ON is the right pick for Ontario. If a form only accepts US states, look for a separate country field and select Canada first.
Canada has ten provinces and three territories. Each has its own two-letter code, such as QC for Quebec and BC for British Columbia. None of them repeat a US state code, which keeps cross border mail sorting simple.
How to address mail to Ontario
Canada Post asks for the city, the province code and the postal code on the same line, with two spaces between the code and the postal code. Canadian postal codes alternate letters and digits in two groups of three, such as A1B 2C3.
Sending a birthday card from the US:
PRIYA SHAH
55 MAPLE CRES
OAKVILLE ON L6J 2X4
CANADA
ON names the province, the postal code beginning with L points to the region around Toronto, and CANADA on the last line tells the US Postal Service where to send it.
Every Ontario postal code begins with one of five letters. K covers the east, including Ottawa. L covers much of the central region. M is the city of Toronto. N is the southwest, and P is the north.
When to use Ont.
Before the two-letter codes, Canadians wrote Ont. on letters, and it still appears in old deeds, library records and some style guides. In running text today, most writers spell out Ontario. Ont. is mainly for tight spaces, such as a chart or a list of cities, when the house style allows it.
- "She grew up in Ontario and moved to Michigan for college."
- "Kingston, Ont., is on Lake Ontario."
- "Province: ON"
Ontario, California and the ONT airport
Searches for an Ontario abbreviation sometimes have nothing to do with Canada. Ontario is also a city in Southern California with its own airport, coded ONT. Travelers flying into the Los Angeles area may choose ONT as an alternative to LAX. A city named Ontario sits in eastern Oregon too.
So if a boarding pass says ONT, you are heading to California, not Toronto. Toronto's main airport has a different code entirely. For a broader list of places and their short forms, see our country, city and airport codes hub.
Look-alike codes to double check
- OH is Ohio, a US state just across Lake Erie from Ontario. One letter off, and a package can land in the wrong country.
- OR is Oregon.
- OK is Oklahoma.
- QC is Quebec, Ontario's neighbor to the east.
A quick memory aid: ON takes the first two letters of Ontario, just as the word itself begins. The O and the N are both right there.
Questions people ask
What is the abbreviation for Ontario?
The official abbreviation is ON, set by Canada Post. The older form, Ont., still appears in some writing.
Is Ontario's abbreviation ON or ONT?
ON is the province code for mail and forms. ONT is the airport code for Ontario, California, a different place.
Is Ontario a state?
No. Ontario is one of Canada's ten provinces. Forms sometimes list it with US states under a State/Province heading.
What does an Ontario postal code look like?
It has six characters in two groups of three, mixing letters and digits, as in K2P 1L4. In Ontario, the first letter is always K, L, M, N or P.