WEBApr 21, 2024 · Guelph, city, seat (1838) of Wellington county, southeastern Ontario, Canada. It lies along the Speed River, 40 miles (65 km) west-southwest of Toronto. Founded in 1827 alongside the falls on the river by John Galt, a Scottish novelist and colonizer, it was named after the Guelfs (Welfs), the family name of the British royal …