This is a list of area codes in the province of Ontario:
- 226: London, Kitchener–Waterloo, Windsor, and most of Southwestern Ontario; overlays with 519
- 249: Most of Northeastern and Central Ontario; overlays 705
- 289: The Niagara Peninsula, Hamilton, Oshawa, and the suburban Greater Toronto Area; overlays with 905 and 365
- 343: Ottawa and surrounding Eastern Ontario; overlays with 613
- 365: The Niagara Peninsula, Hamilton, Oshawa, and the suburban Greater Toronto Area; overlays with 905 and 289
- 416: Toronto; overlays with 647 and 437
- 437: Toronto; overlays with 647 and 416
- 519: London, Kitchener–Waterloo, Windsor, and most of Southwestern Ontario; overlays with 226
- 613: Ottawa and surrounding Eastern Ontario; overlays with 343
- 647: Toronto; overlays with 416 and 437
- 705: Most of Northeastern and Central Ontario; overlays with 249
- 807: Most of Northwestern Ontario
- 905: The Niagara Peninsula, Hamilton, Oshawa, and the suburban Greater Toronto Area; overlays with 289 and 365.
