Matosinhos (Portuguese pronunciation: [mɐtuˈziɲuʃ] ^ⓘ) is a city and a municipality in the district of Porto in Portugal. The municipality covers an area of approximately 62.42 square kilometres (24.10 sq mi) and had 172,557 inhabitants in 2021. It is bordered by the municipalities of Porto to the south, Maia to the east and Vila do Conde to the north and the Atlantic Ocean lies to its west. It is a part of the Porto metropolitan area, the second largest urban area in Portugal.

The city of Matosinhos is the seat of the municipality and it is located at the mouth of the Leça River, only 8 kilometres (5.0 mi) away from Porto's city center. It comprises the parish of Matosinhos and Leça da Palmeira, which had 49,034 inhabitants in 2021. There are two other cities within the municipality, São Mamede de Infesta and Senhora da Hora, in the east of the municipality.

The oldest traces of human settlement in this territory extend back thousands of years and include instruments and Paleolithic artifacts found in beaches such as Boa Nova and Almeiriga. The land's settlement began around 5000 years ago, during the Neolithic, as evidenced from various funeral monuments and dolmens in Lavra, Perafita, Leça do Balio, Santa Cruz do Bispo, Guifões and São Gens.

At the end of the Bronze Age, settlements expanded into castros, proto-urban agglomerations at high altitudes. These existed in the northwestern regions of the Iberian Peninsula and predominated until the 1st century. Remnants of castros remain throughout the municipality, the most notable being Castro of Monte Castelo in Guifões, by the estuary of the Leça river.

After the Roman conquest of the Iberian Peninsula in the 1st century BC, the territory's was developed to support communication and commerce. New roads and bridges were built, including a road between the roman cities of Cale (Porto) and Bracara Augusta (Braga) and Ponte da Pedra, a bridge over the Leça river. The navigability of the estuary of the Leça River permitted goods from the Roman Empire to be discharged in the area of Castro of Monte Castelo and distributed to other sites within the region. Around the 4th and 5th centuries, a Roman villa and salt production and fish salting structures were built in Angeiras (Lavra), in the north of the municipality.

Between the 5th and 7th centuries, the area became a part of the Kingdom of the Suebi and later the Visigothic Kingdom. During this period, Castro of Monte Castelo was abandoned, while the previous Roman settlement in Angeiras remained populated and included a monastery, as referred in the administrative document Parochiale suevorum [pt].

In the 10th century, the Monastery of Bouças was founded in Bouças de Baixo, in the northeast of what is now the city of Matosinhos. It housed the image of Bom Jesus (Good Jesus) of Bouças (nowadays of Matosinhos), an important local religious icon. A settlement gradually formed around the monastery, leading to the creation of the administrative centre of the Julgado de Bouças in the 13th century. Matosinhos itself also dates back to the 10th century, appearing in records as Matesinus, and later as Matusiny, in the 1258 Inquirições of Afonso III. At that time, it was a modest settlement within the parish of Sandim.^{[better source needed]}

Also during the 10th century, the Monastery of Leça do Balio [pt] was established near Ponte da Pedra. In the 12th century, likely between 1112 and 1128, Countess Theresa of Portugal donated the monastery to the Sovereign Military Order of Malta, marking their first foothold in the country. In 1140, King Afonso I granted the order jurisdiction over the parishes of Leça, Custóias, Barreiros, Gueifães and S. Mamede. The order also owned other properties in the region, including the monasteries of Lavra, Moreira and Aldoar.