St. Catharines is a provincial electoral district in Ontario, Canada, that has been represented in the Legislative Assembly of Ontario, first from 1914 to 1934, and again from 1967.

The riding was redrawn in 1999, when Ontario adjusted all of its provincial electoral divisions to match those already existing at the federal level, and has matched the federal riding since.

It currently consists of the part of the City of St. Catharines lying north of a line drawn from west to east along St. Paul Street West, St. Paul Crescent, Twelve Mile Creek, Glendale Avenue, Merrit Street and Glendale Avenue.

The 1999, 2003 and 2007 expenditure entries are taken from official candidate reports as listed by Elections Ontario.

The figures cited are the Total Candidate's Campaign Expenses Subject to Limitation, and include transfers from constituency associations.