The Gateway Arch is a 630-foot (192-meter) stainless steel structure located on the west bank of the Mississippi River in St. Louis, Missouri, United States. It is the world's tallest arch and serves as a symbol of the city of St. Louis and the United States' westward expansion.

The Gateway Arch was designed by Finnish-American architect Eero Saarinen and was completed in 1965. Its design was inspired by the concept of a "gateway to the west", which was popularized in the 19th century when St. Louis served as a major departure point for westward-bound pioneers.

Visitors to the Gateway Arch can take a tram ride to the top of the arch, which provides panoramic views of St. Louis and the surrounding area. The Gateway Arch also features a museum located at its base that explores the history of the westward expansion and the construction of the arch.

In addition to being a major tourist attraction, the Gateway Arch has also become an important symbol of American culture and architecture. It was designated a National Historic Landmark in 1987 and was named one of the "Seven Wonders of the Modern World" by the American Society of Civil Engineers in 1994.