The Vallemaggia District is a district of the canton of Ticino in Switzerland, bordering the Leventina district to the northwest, the Locarno district to the southeast, and Italy to the west. It encompasses eight municipalities and has a population of 5,952 (as of 31 December 2020). The capital of the district is Cevio. Although it extends over approximately one-fifth of the cantonal territory, only about 2% of the Ticino population lived there in 2000.

The district is traversed by the Maggia and its tributaries Bavona and Rovana, and is characterized by two distinct regions. The Valle Maggia comprises the lower valley and the upper valleys (Rovana Valley, Bavona Valley, and Lavizzara Valley). The lower valley, relatively wide, extends from Avegno to Cavergno with minimal elevation changes. The upper valleys are narrow gorges that open into the main valley at Cevio and Bignasco and are surrounded by imposing mountains.

The Vallemaggia District has an area, as of 1997^[update], of 569.42 square kilometers (219.85 sq mi). Of this area, 9.61 km² (3.71 sq mi) or 1.7% is used for agricultural purposes, while 240.5 km² (92.9 sq mi) or 42.2% is forested. Of the rest of the land, 6.57 km² (2.54 sq mi) or 1.2% is settled (buildings or roads), 15.46 km² (5.97 sq mi) or 2.7% is either rivers or lakes and 244.24 km² (94.30 sq mi) or 42.9% is unproductive land.

Of the built up area, housing and buildings made up 0.4% and transportation infrastructure made up 0.4%. Out of the forested land, 31.4% of the total land area is heavily forested and 4.8% is covered with orchards or small clusters of trees. Of the agricultural land, 1.1% is used for growing crops. Of the water in the district, 0.7% is in lakes and 2.0% is in rivers and streams. Of the unproductive areas, 18.9% is unproductive vegetation and 24.0% is too rocky for vegetation.

Isolated findings from the Copper Age attest to prehistoric occupation of the valley. During Romanization, from the final La Tène period to the Augustan era, the population was distributed throughout Val Maggia. Despite its geographical isolation, the valley was connected to the vicus of Muralto. Humans began transforming the landscape through terracing, and the introduction of chestnut and walnut trees during the Roman period.

During the Middle Ages, Val Maggia shared the history of the pieve of Locarno and depended on the church of Saint Victor of Locarno until around the year 1000, when Maggia, Sornico, and Cevio became parishes. Gradually, isolated neighborhood communities (vicinanze) were incorporated into larger units. In the 14th century, Bignasco, Cavergno, Brontallo, and Menzonio formed an administrative entity, as did the villages of Lavizzara and Rovana. Cevio, Cavergno, Campo, Cerentino, and Bosco constituted the Roana Superior.

In 1398, the valleys of Maggia and Verzasca, along with Mergoscia, rebelled against the taxes that the nobles of Locarno, who held fiefs in the region, continuously demanded. They formally separated from the community of Locarno in 1403 and created an independent jurisdiction centered in Cevio, with a General Council of forty-two members and statutes. Several conflicts marked the coexistence of local communities. The dispute that opposed the lower valley communes to Cevio and Val Rovana at the beginning of the 15th century ended with the signing of a treaty in 1403/1404.

Val Maggia attempted to escape the authority of the Duchy of Milan by allying with the House of Savoy (1411-1412), but was occupied by the Confederates (1416), before returning to Milan (1422) and passing to the Rusca family (1439). Around 1430, Val Lavizzara obtained from the Duchy of Milan an independent jurisdiction from Val Maggia.