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Wooden bridge with protective cover

A covered bridge is a timber truss bridge with a roof, decking, and siding, which in most covered bridges create an almost complete enclosure. The purpose of the covering is to protect the wooden structural members from the weather. Uncovered wooden bridges typically have a lifespan of only 20 years because of the effects of rain and sun, but a covered bridge can last over 100 years. In the United States, only about 1 in 10 survived the 20th century. The relatively small number of surviving bridges is due to deliberate replacement, neglect, and the high cost of restoration. Surviving covered bridges often attract touristic attention due to their rarity, quaint appearance, and bucolic settings. Many are considered historic and have been the subject of historic preservation campaigns.

Typically, covered bridges are structures with longitudinal timber trusses which form the bridge's backbone. Some were built as railway bridges, using very heavy timbers and doubled up lattice work. They tend to be in isolated places, making them vulnerable to vandalism and arson.

The oldest surviving truss bridge in the world is the Kapellbrücke in Switzerland, first built in the 1300s. Modern style timber truss bridges were pioneered in Switzerland in the mid 1700s. Germany has 70 surviving historic wooden covered bridges. The Holzbrücke Bad Säckingen spans the river Rhine from Bad Säckingen, Germany, to Stein, Switzerland. It was first built before 1272, and has been destroyed and rebuilt many times. Switzerland has many timber covered bridges, including Kapellbrücke, Spreuer Bridge, and Neubrügg. The Ponte Coperto in Pavia is a stone and brick arch bridge over the Ticino River in Pavia, Italy. The previous bridge, dating from 1354 (itself a replacement for a Roman construction), was heavily damaged by Allied action in 1945. A debate on whether to fix or replace the bridge ended when the bridge partially collapsed in 1947, requiring new construction, which began in 1949.

Most bridges were built to cross streams, and the majority had just a single span. Virtually all contained a single lane. A few two lane bridges were built, having a third, central truss. which enabled him to design stronger bridges with fewer materials.

About 14,000 covered bridges have been built in the United States, mostly in the years 1825 to 1875. However, most other early examples of covered bridges do not appear until the 1820s. Extant bridges from that decade include New York's Hyde Hall Bridge and Pennsylvania's Hassenplug Bridge, both built in 1825, and the Haverhill–Bath Covered Bridge and the Roberts Covered Bridge, in New Hampshire and Ohio respectively, both built in 1829. The longest, historical covered bridges remaining in the United States are the Cornish–Windsor Bridge, spanning the Connecticut River between New Hampshire and Vermont, and Medora Bridge, spanning the East Fork of the White River in Indiana. Both lay some claim to the superlative depending upon how the length is measured. In the mid 1800s, the development of cheaper wrought iron and cast iron led to metal rather than timber trusses. Metal structures did not need protection from the elements, so they no longer needed to be covered. The bridges also became obsolete because most were single lane, had low width and height clearances, and could not support the heavy loads of modern traffic. mostly in eastern and northern states. The 2021 World Guide to Covered Bridges lists 840 covered bridges in the U. S., although it states that only 670 of those were standing when the 1959 edition was published. The tallest (35 feet high), built in 1892, is the Felton Covered Bridge, just north of Santa Cruz, California. In 1900, Quebec had an estimated 1,000 covered bridges. Relative to the rest of North America, Quebec was late in building covered bridges, with the busiest decade for construction being the 1930s. Initially, the designs were varied, but around 1905, the design was standardised to the Town québécois, a variant on the lattice truss patented by Ithiel Town in 1820. The designer is unknown. About 500 of these were built in the first half of the 1900s. In Quebec covered bridges were sometimes known as pont rouges (red bridges) because of their typical colour. Ontario has just one remaining covered bridge, the West Montrose Covered Bridge.

Roofed, rather than covered bridges, have existed for centuries in southern Europe and Asia. In these cases, the cover is to protect the users of the bridge rather than the structure. Examples include:
The Pont de Rohan in Landerneau, France, and the Pont des Marchands in Narbonne are two of 45 inhabited bridges in Europe. A tubular bridge is a bridge built as a rigid box girder section within which the traffic is carried. Examples include the Britannia Bridge and the Conwy Railway Bridge in the United Kingdom. A skyway is a type of urban pedway consisting of an enclosed or covered footbridge between two buildings, designed to protect pedestrians from the weather. For example, the Bridge of Sighs in Cambridge, and Oxford's Bridge of Sighs and Logic Lane covered bridge. A jet bridge is an enclosed, moveable bridge which extends from an airport terminal gate to an airplane, allowing passengers to board and disembark without having to go outside. Some stone arch bridges are covered to protect pedestrians or as a decoration—as with the Italian Ponte Coperto and Rialto Bridge, and the Chùa Cầu (the Japanese Bridge; see Gallery below) in Vietnam. In China lángqiáo (廊桥) covered bridges are found in Guangxi, including the Chengyang Bridge and the Xijin Bridge. These are pier and girder bridges, not truss bridges. The Chùa Cầu bridge is found in Vietnam. In Europe there are also bridges built not strictly for transport, for example the Český Krumlov Castle Bridge in the Czech Republic, the Lovech Covered Bridge in Bulgaria, and the Ponte Vecchio in Italy.