Thorold (2001 population 18,048) is a city on the Welland Canal and the seat of the Niagara Region in Ontario, Canada.

The canal goes right through the heart of the city, and the lock in the centre of town attracts thousands of tourists a year.

Many regard Thorold as nothing more than a southern suburb of the much larger City of St. Catharines, much to the dismay of local Thorold residents who fight hard to preserve their local identity. Threat of annexation by St. Catharines led to Thorold incorporating as a city in 1975.

The city was first incorporated in 1850 and became a city in 1975.

Communities

• Allanburg
• Port Robinson
• St. John's
• Thorold
• Thorold South
• Turner's Corners