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 2021 was 67,709, in an area of 136.60 square kilometres. Another important center in the municipality is Aves. The Santo Tirso Monastery built in 978 is a point of interest.