Rochester () is a city in the U.S. state of New York, the seat of Monroe County, and the fourth-most populous in the state after New York City, Buffalo, and Yonkers, with a population of 211,328 at the 2020 United States census. Located in Western New York, the city of Rochester forms the core of a larger metropolitan area with a population of 1 million people, across six counties.

The city was one of the United States' first boomtowns, initially due to the fertile Genesee River Valley, which gave rise to numerous flour mills, and then as a manufacturing center, which spurred further rapid population growth.Rochester rose to prominence as the birthplace and home of some of America's most iconic companies, in particular Eastman Kodak, Xerox, and Bausch & Lomb (along with Wegmans, Gannett, Paychex, Western Union, French's, Constellation Brands, Ragú, and others), by which the region became a global center for science, technology, and research and development.

This status has been aided by the presence of several internationally renowned universities (notably the University of Rochester and Rochester Institute of Technology) and their research programs; these schools, along with many other smaller colleges, have played an increasingly large role in Greater Rochester's economy.

Rochester has also played a key part in US history as a hub for certain important social and political movements, especially abolitionism and the women's rights movement.Today, Rochester's economy is defined by technology and education (aided by a highly educated workforce, research institutions, and other strengths born in its past).

While the city experienced some significant population loss as a result of deindustrialization, strong growth in the education and healthcare sectors boosted by elite universities and the slower decline of bedrock companies such as Eastman Kodak and Xerox (as opposed to the rapid fall of heavy industry with steel companies in Buffalo and Pittsburgh) resulted in a much less severe contraction than in most Rust Belt metro areas.

The Rochester metropolitan area is the third-largest regional economy in New York, after the New York City metropolitan area and the Buffalo-Niagara Falls Metropolitan Area. Rochester's gross metropolitan product is US$50.6 billion—above those of Albany and Syracuse, but below that of Buffalo.Rochester is also known for its culture, in particular its music culture; institutions such as the Eastman School of Music (considered to be one of the most prestigious conservatories in the world) and the Rochester International Jazz Festival anchor a vibrant music industry, ranked as one of the top-10 music scenes in the US in terms of the concentration of musicians and music-related business.

It is the site of multiple major festivals every year (such as the Lilac Festival, the aforementioned Jazz Festival, the Rochester Fringe Festival, and others that draw hundreds of thousands of attendees each) and is home to several world-famous museums such as The Strong National Museum of Play and the George Eastman Museum, which houses the oldest photography collection in the world and one of the largest.The Rochester metro is ranked highly in terms of livability and quality of life and is often considered to be one of the best places in America for families due to low cost of living, highly ranked public schools and a low unemployment rate.

It is considered to be a global city, ranked by the Globalization and World Cities Research Network as having sufficiency status.