Hamilton joins the growing list of municipalities that have approved a mandatory mask by-law.
Masks or face coverings will be required in indoor public and commercial spaces.
The new rules go into effect on Monday, July 20.
In Niagara, St. Catharines mandatory mask by-law came into effect today, Niagara-on--the-lake's will take effect next Thursday.
The Niagara Region will debate the matter again on Thursday in a special session set for 4 p.m.
Niagara Falls council briefly discussed the issue at a council meeting Tuesday, but opted to defer to the Region for a decision.
Toronto, Ottawa, Halton Region, Peel and Durham Region, Brant Country, Brantford, Kawartha Lakes &, Simcoe-Muskoka have all passed mandatory bylaws.
Many more Ontario municipalities intend to deal with the issue next week.