Martigny serves as the capital city of the Martigny district within the canton of Valais, Switzerland. Situated in the French-speaking part of the country, it lies at an elevation of 471 meters on the left foothills of the steep Rhone Valley. The town occupies a strategic geographic position where the southwestern-flowing Rhone turns ninety degrees northward toward Lake Geneva, with the La Drance river joining from the south. It functions as a vital junction connecting Italy, France, and Switzerland via major road routes over the Great St. Bernard Pass and the col de la Forclaz.

The settlement originated in the first century BC as Octodurus, an oppidum of the Veragri Gauls, before being conquered by the Roman Republic in 57 BC. Following a period of decline, a new Roman colony named Forum Claudii Vallensium was established nearby around AD 41 to serve as the provincial capital. The town later adopted the German name Martinach and became known by its current French name after taking Saint Martin of Tours as its patron saint in the Middle Ages. It was granted autonomy under the House of Savoy in 1351 before passing to Switzerland in 1815.

The modern municipality was formed in 1964 through the merger of Martigny-Ville and Martigny-Bourg, with Charrat merging in 2021. The area features significant Roman heritage, including a restored amphitheatre, temples, and thermal baths, alongside medieval structures like La Bâtiaz Castle. Several sites hold national significance, such as the Centre valaisan du film and three museums dedicated to Gallo-Roman history, automobiles, and the artist Pierre Gianadda. The entire town of Martigny-Ville and the small town of Martigny-Bourg are listed in the Inventory of Swiss Heritage Sites.

Martigny attracts visitors with its rich historical layers and proximity to winter sports destinations like Verbier. Cultural attractions include the Museum of St. Bernard, which showcases the local dog breed, and the Fondation Pierre Gianadda, which hosts art exhibitions and permanent displays on the city's Roman past. The town also offers unique experiences such as walks with Saint Bernard dogs at the Fondation Barry. Its economic base traditionally relied on agriculture and viticulture, though it now serves as one of the region's primary economic centers.

As of 2018, Martigny had a population of 18,301 inhabitants. The local economy benefits from its role as a transport hub, connected to the Simplon railway since 1878 and the Swiss motorway system via the A9 since 1981. Trains run every thirty minutes between Geneva and Brig, while the Mont Blanc Express provides hourly service from Chamonix. The town is known for its numerous nearby Alpine ski resorts in winter, drawing tourists to the region for both cultural exploration and outdoor activities.