Worcester ( WUUST-ər, locally [ˈwɪstə] ) is the 2nd most populous city in the U.S. state of Massachusetts and the 114th most populous city in the United States. Named after Worcester, England, the city's population was 206,518 at the 2020 census, also making it the second-most populous city in New England after Boston. Worcester is approximately 40 miles (64 km) west of Boston, 50 miles (80 km) east of Springfield and 40 miles (64 km) north-northwest of Providence. Due to its location near the geographic center of Massachusetts, Worcester is known as the "Heart of the Commonwealth"; a heart is the official symbol of the city. Worcester is the historical seat of Worcester County in central Massachusetts.

Worcester developed as an industrial city in the 19th century due to the Blackstone Canal and rail transport, producing machinery, textiles and wire. Large numbers of European immigrants made up the city's growing population. However, the city's manufacturing base waned following World War II. Long-term economic and population decline was not reversed until the 1990s, when higher education, medicine, biotechnology, and new immigrants started to make their mark. The city's population has grown by 28% since 1980, reaching a new all-time high in the 2020 census and experiencing urban renewal.

Modern Worcester is known for its diversity and large immigrant population, with significant communities of Vietnamese, Brazilians, Albanians, Puerto Ricans, Ghanaians, Dominicans, and others. Twenty-two percent of Worcester's population was born outside the United States. A center of higher education, it is home to eight separate colleges and universities, including the College of the Holy Cross, Worcester Polytechnic Institute (WPI), and Clark University. Architecturally, Worcester is notable for its large number of 19th-century triple-decker houses, Victorian-era mill architecture, and lunch car diners such as Miss Worcester.

Worcester is the principal city of Central Massachusetts, and is a regional government, employment and transportation hub. Since the 1970s, and especially after the construction of Route 146 and interstates 90, 495, 190, 290, and 395, both Worcester and its surrounding towns have become increasingly integrated with Boston's suburbs. The Worcester region now marks the western periphery of the Boston–Worcester–Providence (MA–RI–NH) U.S. Census Combined Statistical Area (CSA), or Greater Boston.