The Union Labor Party was a political party in the United States during the late nineteenth century. The party was organized at Cincinnati in 1887 as a merger of several agrarian, socialist, and trade union groups, following the success of state and municipal labor parties in the 1886 United States elections. The national party ran Alson Streeter in the 1888 United States presidential election. After 1891, the party was absorbed into the new People's Party.

In 1884, in Milwaukee, the Milwaukee Trades' Assembly organized a merger of the Greenback Labor Party (GLP) and Anti-Monopoly Party (AMP) into a local People's Party (PP), often called the Populists. This merger was strongly supported by the local socialists.^{[citation needed]}

During the mid-1880s, Knights of Labor (K of L) organizer Robert Schilling had organized more than 40 lodges with over 25,000 members. The K of L and the more radical Central Labor Union, led by Paul Grottkau, agitated heavily for an eight-hour day. In 1886, after the Bay View massacre of a pro-eight-hour rally in Milwaukee and Haymarket affair in Chicago, anti-labor sentiment rose dramatically into a national "red scare". The Milwaukee city council repealed its eight-hour ordinance and a Milwaukee grand jury indicted Schilling, Grottkau, and 47 other men. In response to this repression, the K of L and Schilling took control of the People's Party, which quickly denounced the use of violence by both "fanatical anarchists" and "corrupt politicians" and demanded that "land, money, the means of communication and all public improvements [....] should be owned and controlled by the people."

The Haymarket affair and other red scare repressions led to wave of pro-labor organizing. For example, in New York, the United Labor Party was organized by numerous local unions and left-wing groups, including the CLU, K of L, and the Socialist Labor Party (SLP), and ran Henry George for the 1886 mayoral election. In 34 of 38 states, 4 territories, and 189 towns, workers created a Union Labor Party, United Labor Party, or other similarly-named organization. Historian Leon Fink, describing this era, said that it "may still stand as the American worker’s single greatest push for political power".

At first, the ULP saw striking success, greater than that of any prior US labor party.

In the 1886 elections, the Populists obtained considerable successes, especially in Milwaukee. The Populists elected several members to both the Wisconsin Senate and State Assembly, including Populist president Michael P. Walsh. In the gubernatorial election, the Populist's candidate, John Cochrane, won 7.50% of the vote. In the US House elections, the Populists successfully elected Henry Smith in WI-4 over both a Republican and a Democratic opponent.

Also during the 1886 elections, Samuel I. Hopkins, a Confederate veteran, was elected to Virginia's 6th Congressional District with 51.6% of the vote.

These election victories encouraged the labor movement. Schilling re-organized the People's Party into the Union Labor Party (ULP), which began to organize a fledgling country-wide political apparatus, appointing regional representatives from the Knights of Labor, trade unions, Grangers, the Anti-Monopoly Party, and other pro-labor elements.