The Boulevards of the Marshals (French: Boulevards des Maréchaux, pronounced [bulvaʁ de maʁeʃo]) are a series of traffic arteries that together encircle the city of Paris, France, just inside its city limits. Development of the Boulevards began in the 1860s under Napoleon III who named nineteen of them after a Marshal who served under his uncle, Napoleon I. Never officially designated as a thoroughfare, the name came into gradual use during the 20th century as the work was completed and the various segments came to be perceived as a whole.

From 1951 to the early 2000s, the circuit was served by the PC (Petite Ceinture: small beltway) buses. They have since been replaced by the Tramway des Maréchaux (Île-de-France tramway Lines 3a and 3b) except in the 16th arrondissement.

The Boulevards of the Marshals occupy the route of the former Rue Militaire (Military Road), built in the 1840s as part of the new Thiers Fortifications which circled Paris. Adjacent to the inner perimeter of the walls and bastions, the Rue was a service road used to transfer soldiers and deliver supplies. During the 1850s, work began on a modern replacement, the Chemin de fer de Petite Ceinture ("Smaller Belt Railway"), its path typically 100 meters further inside, and which in peacetime would transport merchandise and passengers between the capital's six mainline railway stations.

Relegated to a secondary role in the city's defense, the Rue Militaire became part of Haussmann's effort to improve Paris’ arterial streets. In 1859 the city obtained from the Army the right to improve and maintain it, with the intention to widen it to six meters, pave it, and build sidewalks. In 1861, after the annexation of the outer districts that expanded the city limits to the fortifications, the city secured authorization to widen the Rue to the standard boulevard forty meters, expropriating civilian property inside the loop if necessary. In 1864, amidst the deluges of new street designations for the city, the Rue Militaire was divided into 19 sections, each a Boulevard named after a Marshal of Napoleon I. Such reflected Napoleon III's practice of anchoring the legitimacy of his regime on the Bonaparte family, particularly his famous uncle. They were to be a “ring road boulevard” (boulevard de ceinture), but no collective name was ever officially given.

Whatever the initial ambitions, only a few short stretches of the military service road were rebuilt as actual boulevards during the Second Empire. However, much work was done on the circuit over the next thirty years with the goal of encouraging development in the less populated outer districts. In 1919 the fortifications were ceded to the city and demolished over the following decade, prompting further improvements of the Boulevards to accommodate anticipated development of the newly available real estate as well as the advent of the automobile. By 1939, all the boulevards had the 20-meter central carriageways envisaged 80 years before. From the 1930s, the Boulevards were served by the PC bus. The range of the automobile and the bus fostered the notion that the segments had become a single, circular thoroughfare comparable to the Grands Boulevards in central Paris, or the Exterior Boulevards whose path was followed by Metro Lines 2 and 6.  

After World War II, faced with the sharp growth of automobile usage and growing traffic volume, Paris embraced the motorway. The Boulevards of the Marshals, now heavily used, were quickly judged to be inadequate. Between 1956 and 1973 a new ring-road, the Boulevard Périphérique, was built on the 250 meter-wide field-of-fire belt outside the now-demolished fortifications. A pedestrian-free, limited access motorway designed for high-speed driving, few referred to Le Périph as a boulevard, and it had little in common with its 19th century predecessor. Moreover, as congestion proved unrelenting, the Boulevards of the Marshals were reengineered in an effort to permit their traffic to approach motorway speeds and volume: widening the carriageway, reducing the number of traffic lights and pedestrian crossings, and building underpasses under major intersections.

In the closing years of the 20th century, Paris began changing its automobile policies, including restricting parking, promoting mass transit and cycling, and redesigning its traffic arteries. In the early 2000s, much of the Boulevards of the Marshals were rebuilt to create a more pedestrian-friendly environment, focused on new tramways along 85% of its circuit. The stated objectives of the tramway and the latest remake of the Boulevards were to provide more public transport capacity than the PC buses, reduce the presence of cars and related services, reclaim public space, stimulate commercial and community life, and narrow the livability gap as compared with Paris’ poorer suburbs.

The Boulevards of the Marshals concept was adulterated just as it was coming to fruition. In 1932, during a period of renewed attention to the French Navy, a section of Boulevard Lannes was renamed Boulevard de l’Amiral Bruix. Étienne Eustache Bruix was a high-ranking naval officer and administrator under the Directory and Consulate, but not a marshal or its naval equivalent. In 1987, a section of Boulevard Victor was renamed Boulevard du Général-Martial-Valin. Valin was commander of the Free French air force, a hero of the liberation of Paris, and served in other high military posts until the 1960s. In 2005, a section of Boulevard Masséna was renamed the Boulevard du General-Jean-Simon. Simon had a distinguished military career with the Free French and the postwar army, and in the late 20th century was a prominent figure in various civic and military associations honoring the Liberation. Neither Valin nor Simon was granted the distinction of Marshal.