Worcester ( WUUST-ər, locally [ˈwɪstə] ) is the second-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 had 206,518 people at the 2020 census, also making it the second-most populous city in New England, after Boston, Massachusetts. Worcester is about 40 miles (64 km) west of Boston, 50 miles (80 km) east of Springfield, Massachusetts, and 40 miles (64 km) north-northwest of Providence, Rhode Island. Because it is 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.

Worcester developed as an industrial city in the 19th century because the Blackstone Canal and railways facilitated the import of raw materials and the export of such finished goods as machines, textiles, and wire. Many European immigrants made up the city's growing population. After World War II, manufacturing there waned; economic and population decline was not reversed until the 1990s, when higher education, medicine, biotechnology, and new immigrants started making their mark. The population has grown by 28% since 1980, reaching its all-time high in the 2020 census and effecting urban renewal.

Modern Worcester is known for its diversity and large immigrant population, with significant communities of Vietnamese, Brazilians, Albanians, Puerto Ricans, Ghanaians, Dominicans, Irish, English, Italians, Greeks, 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 colleges and universities, including the College of the Holy Cross, Worcester Polytechnic Institute (WPI), Clark University, and Worcester State University. Worcester has many 19th-century triple-decker houses, Victorian-era mills and related buildings, and lunch-car diners, such as Miss Worcester.

Worcester is the principal city of Central Massachusetts, and is a regional hub of government, industry, and transportation. Since the 1970s, and especially since the construction of Route 146 and interstates 90, 495, 190, 290, and 395, both Worcester and its surrounding towns have become more 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.