A covered bridge is a timber-truss bridge complete with a roof, decking, and siding, which in most cases creates an almost complete enclosure. The purpose of the covering is to protect the wooden structural members from the the effects of rain and sun, effectively increasing the lifespan of the bridge from about twenty years when not covered to about 100 years when it is covered.

In the United States, the survival rate of covered bridges is about ten percent because only about 1 out of 10 survived into the 21st century. The relatively small number of surviving bridges is due in part to deliberate replacement, neglect or the high cost of restoration.

The state of Pennsylvania has 219 historic covered bridges.