Gentrification, or urban gentrification, is the change in an urban area associated with the movement of more affluent individuals into a lower-class area. The area experiences demographic shifts, including an increase in the median income, a reduction in household size, and often a decline in the proportion of lower-class groups. More households with higher incomes result in increased real estate values with higher associated rent, home prices, and property taxes. Industrial land use can decline with redevelopment bringing more commercial and residential use. Such changes often result in transformation of the neighborhood's character and culture.

Gentrification can result from reinvestment efforts or neighborhood groups, which directs money to invest in crime ridden cities' infrastructure, offer incentives for redevelopment, improve access to housing loans for low-income mortgage seekers, assist lending to first-time home purchasers, and improve rental properties. These efforts have been linked to reductions in local property crime rates, increased property prices, increased revenue to local governments from property taxes and increased tolerance of gay people. Grassroots efforts for existing residents to guide or oppose gentrification generates community activism.

The process has a human cost to the neighborhood's lower-income residents. The increases in rent often result in the dispersal of communities whose members find that housing in the area is no longer affordable. Additionally, the increase in property taxes (due to increased property values) may sometimes force or give incentive for homeowners to sell their homes and move to less expensive neighborhoods. While those who view gentrification positively cite local reductions in a neighborhood's property crime rate, its critics argue that overall crime rates have not actually been reduced, but merely shifted to different lower-income neighborhoods.

The concept of gentrification has received significant attention in a number of academic disciplines, most notably urban geography and urban sociology. Some academics argue that the concept has become so broad as to lose its applicability. Others, however, contend that it has become the fundamental idea for understanding market-driven urban class relations.