A megaproject is an extremely large-scale investment project. Megaprojects are typically defined as costing more than US$1 billion and attracting a lot of public attention because of substantial impacts on communities, environment, and budgets. Megaprojects can also be defined as "initiatives that are physical, very expensive, and public". Care in the project development process may be needed to reduce any possible optimism bias and strategic misrepresentation. The logic on which many of the typical mega-projects are built is on its collective benefits, for example electricity for everybody (who can pay), road access (for those that have cars), etc. Mega-projects have undergone a wide criticism for its top down planning process and for its ill effects on certain communities. From the 1960s on, mass mobilization took place against the building of inner city freeways in North America (for example in New York City, Toronto, Seattle, San Francisco), or nuclear power plants in the US and Germany, or proposal for new airports such as Mexico City in 2001. More recently, new types of mega-projects have been identified that no longer follow the old models of being singular and monolithic in their purposes, but now have become quite flexible and diverse, such as waterfront redevelopment schemes that seem to offer something to everybody. However, just like the old mega-project, the new ones also foreclose "upon a wide variety of social practices, reproducing rather than resolving urban inequality and disenfranchisement". Because of its plethora of land uses "these mega-projects inhibits the growth of oppositional and contestational practices". The collective benefits that are often the underlying logic of a mega-project, are here reduced to an individualized form of public benefit.
Megaprojects include bridges, tunnels, highways, railways, airports, seaports, power plants, dams, wastewater projects, Special Economic Zones, oil and natural gas extraction projects, public buildings, information technology systems, aerospace projects, weapons systems and, more recently, large-scale mixed use waterfront redevelopments; however, the most common megaprojects are in the categories of hydroelectric facilities, nuclear power plants and large public transportation projects.
Investing in megaprojects in order to stimulate the general economy has been a popular policy measure since the economic crisis of the 1930s. Recent examples are the 2008-2009 Chinese economic stimulus program, the 2008 European Union stimulus plan, and the American Recovery and Reinvestment Act of 2009.
See also 
- Alan Altshuler and David Luberoff, Mega-Projects: The Changing Politics of Urban Public Investment (Washington, DC: Brookings Institution, 2003). ISBN 0-8157-0129-2
- Lehrer, U. and J. Laidley. 2008. “Old Mega-projects Newly Packaged? Waterfront Redevelopment in Toronto”, International Journal for Urban and Regional Research, 32(4) 786-803