The Reading Railroad Massacre occurred on July 23, 1877, when strikes in Reading, Pennsylvania, led to an outbreak of violence, during which 10 to 16 people were killed and between 20 and 203 were injured. It was the climax of local events during the Great Railroad Strike of 1877 towards the end of the Long Depression of 1873–1879, following arson and riots against local facilities of the Philadelphia and Reading Railway.

Units of the Pennsylvania State Militia were brought in by train. Near nightfall, one unit was marched into the Seventh Street Cut, a man-made ravine three blocks long with 20-or-30-foot (6.1 or 9.1 m) walls, to free a train that had been stopped by rioters. The soldiers were bombarded from above with bricks, stones, and gunshots, and some of the soldiers fired rifle volleys into a crowd at the far end of the Cut. Between 10 and 16 civilian deaths resulted, along with dozens of injuries. Most rioting ended that night, and tense quiet prevailed the next day. Ultimately, the arrival of federal troops restored order to Reading. A coroner's inquest following the massacre did not blame the militia for the deaths, but pointed to the overall upheaval in the city at the time. Blame was laid upon the local sheriff for failing to keep the public order.

The Long Depression, sparked in the United States by the Panic of 1873, had extensive implications for US industry, closing more than a hundred railroads in the first year and cutting construction of new rail lines from 7,500 miles (12,100 km) of track in 1872 to 1,600 miles (2,600 km) in 1875. Approximately 18,000 businesses failed between 1873 and 1875, production in iron and steel dropped as much as 45 percent, and a million or more lost their jobs. In 1876, 76 railroad companies went bankrupt or entered receivership in the US alone, and the economic impacts rippled through many economic sectors throughout the industrialized world.

In mid-1877, tensions erupted in stoppages and civil unrest across the nation in what became known as the Great Railroad Strike or the Great Strikes. Violence broke out in Martinsburg, West Virginia, and spread along the rail lines through Baltimore and on to several major cities and transportation hubs of the time, including Reading, Scranton, and Shamokin, Pennsylvania; a bloodless general strike in St. Louis, Missouri; and a short lived uprising in Chicago, Illinois. In the worst case, rioting in Pittsburgh, Pennsylvania, left 61 dead and 124 injured. Much of the city's center was burned, including more than a thousand rail cars destroyed. What began as the peaceful actions of organized labor attracted the masses of discontented and unemployed workers spawned by the depression, along with others who took opportunistic advantage of the chaos. In total, an estimated 100,000 workers participated nationwide.

In 1877, the city of Reading was largely controlled by the Philadelphia and Reading Railway under Franklin B. Gowen. The town was heavily reliant on rail along with the Philadelphia and Reading Coal and Iron Company. There was a general doubt as to whether conditions existed for serious labor troubles. At one point, the Pottsville Miners Journal wrote in an editorial that "the men have no organization, and there is too much race jealousy existing among them to permit them to form [a strike]".

Reading had seen strikes for a time. In early 1877, members of the Brotherhood of Locomotive Engineers and Trainmen had requested a raise. When the railroad refused, and "the men had no choice but to strike", the railroad effectively crushed the trade union. They issued a letter telling their employees that, of those who were members of the Brotherhood, "It has been deemed unadvisable to retain in the employment of this Company any one who is a member of that organization," issuing an ultimatum that they would either leave the union or lose their jobs. Many citizens of Reading were subsequently fired and blacklisted. Others who were still employed by the company were owed back wages, and had not been paid since the end of strikes in May, but they were eventually paid on July 20.

Throughout much of the early strikes elsewhere, there was little unrest in the town. Upon the start of strikes nationwide on July 16, the town remained relatively calm, to the point that the mayor left on a vacation to Ocean Grove, New Jersey.

Violence broke out on July 22, 1877, when a car filled with roof shingles was set ablaze on a railroad siding, near the corner of Elm Street and 7th Street. A crowd of over two thousand people took the depot, and burned "two cabooses, seven freight cars, and the watch house at the Reading and Lehigh Railroad junction at Bushong’s Furnace". As a result of the ongoing unrest throughout Pennsylvania, the state militia was assembling to travel to the Pennsylvania State Capitol in Harrisburg, under order of the governor. In order to prevent the militia from reaching the capitol, a group of rioters set fire to the Lebanon Valley Branch bridge over the Schuylkill River. The bridge was completely destroyed, with only the brick piers remaining. Rail travel with Harrisburg was blocked, the telegraph lines were damaged, and the debris halted passage both up and down the Schuylkill. The damage was estimated at $150,000 (equivalent to $4,535,000 in 2025).