Los Angeles Union Station is the main railway station in Los Angeles, California, and the largest railroad passenger terminal in the Western United States. It opened in May 1939 as the Los Angeles Union Passenger Terminal, replacing La Grande Station and Central Station.

Approved in a controversial ballot measure in 1926 and built in the 1930s, it served to consolidate rail services from the Union Pacific, Santa Fe, and Southern Pacific Railroads into one terminal station. Conceived on a grand scale, Union Station became known as the "Last of the Great Railway Stations" built in the United States. The structure combines Art Deco, Mission Revival, and Streamline Moderne style. It was placed on the National Register of Historic Places in 1980.

Today, the station is a major transportation hub for Southern California, serving almost 110,000 passengers a day. It is by far the busiest train station in the Western United States; it is Amtrak's fifth-busiest station, and is the twelfth-busiest train station in North America.

Four of Amtrak's long-distance trains originate and terminate here: the Coast Starlight to Seattle, the Southwest Chief and Texas Eagle to Chicago, and the Sunset Limited to New Orleans. The state-supported Amtrak Pacific Surfliner regional trains run frequently to San Diego and also to Santa Barbara and San Luis Obispo. The station is the hub of the Metrolink commuter rail system and is a major transfer point for several Metro Rail subway and light rail lines. The Patsaouras Transit Plaza, on the east side of the station, serves dozens of bus lines operated by Metro and several other municipal carriers.