Santo Tirso is a city and municipality located in the north of Porto Metropolitan Area, 25 km from central Porto, Portugal. In the region, the Ave Valley, there is a large center of textile industry. The population in 2011 was 71,530, in an area of 136.60 km².
Another important center in the municipality is Aves.
The Santo Tirso Monastery built in 978 is a point of interest.