Greater Boston means both a metropolitan statistical area (MSA) and a combined statistical area (CSA), which is broader. The MSA includes most of the eastern third of Massachusetts, but not the south-eastern part of the state, as well as south-eastern New Hampshire. The CSA includes the eastern two-thirds of Massachusetts, southern New Hampshire, and all of Rhode Island. It includes the Providence (Rhode Island), Manchester (New Hampshire), and Worcester (Massachusetts) areas.
The city of Boston covers 48.4 square miles (125 km2) and 675,647 live there as of 2020. Some of the adjacent areas are also urban, with many people living close together. The Greater Boston MSA has 4.9 million people as of 2020. It is the 11th largest in the country. The CSA has more than 8.4 million people. The Greater Boston CSA is one of two combined statistical areas in Massachusetts - the other one is around Springfield.
It is the northern part of the Northeast megalopolis, a chain of nearby cities and towns.