ऐसी परियोजना को महापरियोजना या मेगाप्रोजेक्ट (megaproject) कहते हैं जिसमें अत्यन्त बड़े स्तर निवेश (investment) करने की जरूरत पड़ती है। प्राय: एक बिलियन अमेरिकी डालर से भी अधिक खर्च वाले परियोजनाओं को महापरियोजना की श्रेणी में रखा जाता है। इन पर जनता का बहुत ध्यान भी आकर्षित होता है क्योंकि इनका आम जनता, पर्यावरण एवं देश की अर्थव्यवस्था पर बड़ा असर पड़ने की सम्भावना रहती है। दूसरे शब्दों में महापरियोजना उस पहल (इनिशिएटिव) को कहते हैं जिनमें कुछ भौतिक चीज बनने वाली हो, जो बहुत खर्चीली हो और जो सार्वजनिक हो। 

पुल, सुरंग, राजमार्ग, रेलपथ, हवाई अड्डे, समुद्री पत्तन, उर्जा संयंत्र, बांध, विशेष आर्थिक क्षेत्र (SEZ), तेल एवं प्राकृतिक गैस निकालना, वायु-अन्तरिक्ष परियोजना, अस्त्र-प्रणाली परियोजना आदि महापरियोजना की श्रेणी में आ सकतीं हैं।

उदाहरण 
नीचे महापरियोजनाओं के प्रमुख उदाहरण दिये गये हैं-

वायु-अन्तरिक्ष परियोजनाएँ 

 चन्द्रयान, (भारत) (२००९)
 एयरबस ए380 (2007)
 B-2 Spirit (1997)
 बोइंग 747 (1970)
 Eurofighter Typhoon (2003)
 F-22 Raptor (2005)
 Joint Strike Fighter (In progress)
 KH-11 reconnaissance satellite (1976-1990)

हवाई अड्डे की परियोजनाएँ 

 Abu Dhabi International Airport, Abu Dhabi, United Arab Emirates
 Alcochete Airport, Portugal
 Athens International Airport, Athens, Greece
 Indira Gandhi International Airport, New Delhi, India
 Chhatrapati Shivaji International Airport, Mumbai, India
 Beijing Capital International Airport, Beijing, People's Republic of China
 Berlin-Brandenburg International Airport, Berlin, Germany
 Cape Town International Airport, Cape Town, South Africa
 Denver International Airport, Denver, Colorado, USA
 Diosdado Macapagal International Airport, Angeles City, Philippines
 Dubai International Airport, Dubai, UAE
 Dubai World Central International Airport, Jebel Ali, UAE
 Frankfurt Airport, Frankfurt am Main, Germany
 Guangzhou Baiyun International Airport, Guangzhou, People's Republic of China
 Incheon International Airport, Incheon, South Korea
 Hartsfield-Jackson Atlanta International Airport, Atlanta, Georgia, USA
 Hong Kong International Airport, Hong Kong, China
 Kansai International Airport, Japan
 King Shaka International Airport, Durban, South Africa
 Kuala Lumpur International Airport, Malaysia
 London Heathrow Airport, Terminal 5, London, UK
 Long Thanh International Airport, Vietnam
 Madrid Barajas International Airport, Madrid, Spain
 O'Hare International Airport, Chicago, Illinois, USA
 OR Tambo International Airport, Johannesburg, South Africa
 Suvarnabhumi Airport, Bangkok, Thailand
 New Doha International Airport, Doha, Qatar

भवन परियोजनाएँ 

 World Trade Center, New York City, New York (1973)
 Berlin Hauptbahnhof (Central Station), Berlin, Germany (2006)
 बुर्ज खलीफा, दुबई, संयुक्त अरब अमीरात (2009)
 Governor Nelson A. Rockefeller Empire State Plaza, Albany, New York, USA (1978)
 Cowboys Stadium in Arlington, Texas, USA (2009)
 Pagcor Tower, Manila, Philippines (Est. 2012)
 Jakarta Tower, Jakarta, Indonesia (Est. 2011)
 Palace of the Parliament, Bucharest, Romania (1989)
 Parliament House, Canberra, Australia (1988)
 Petronas Twin Towers, Kuala Lumpur, Malaysia (1998)
 Sydney Opera House, Australia (1973)
 Taipei 101, Taipei, Taiwan, ROC (2004)
 The new Wembley Stadium in London, UK (2007)
 CN Tower, Toronto, Canada (1976)
 Sears Tower, Chicago, USA (1973)
 Empire State building, New York City, USA (1931)

नहर परियोजनाएँ 

 Arabian Canal, United Arab Emirates
 Danube-Black Sea Canal, Romania
 Erie Canal, New York
 Grand Canal, China
 Grand Korean Waterway
 Kiel Canal, Germany
 पनामा नहर, पनामा
 स्वेज नहर, मिश्र
 Welland Canal, Ontario, Canada
 Sanitary and Ship Canal, Chicago, Illinois
 सेतु नहर, भारत

बांध परियोजनाएँ 

 Aswan Dam, Egypt
 Katse Dam, Lesotho
 Alqueva, Portugal
 Hoover Dam, USA
 Itaipu, Brazil/Paraguay
 Sayano–Shushenskaya Dam, Russia (1961-78)
 Three Gorges Dam, China
 Tennessee Valley Authority, USA
 The Kárahnjúkar Hydropower Project, Iceland
 Tehri Dam, India
 Bakun Dam, Sarawak
 Bhakra Dam, India

रक्षा परियोजनाएँ 

 चीन की महान दीवार
 Maginot Line
 Hadrian's Wall, UK
 स्टार वार (Strategic Defense Initiative) (कभी पूर्णत: लागू नहीं हुई)
 मैनहट्टन परियोजना
 Željava Air Base

अन्तरराष्ट्रीय खेलकूद की परियोजनाएँ 
 Cricket World Cup
 FIFA World Cup
 Olympic Games
 Rugby World Cup

सूचना तकनीकी परियोजनाएँ 
 Enabling Grids for E-sciencE: Multi-science Grid infrastructure for the European Research Area. Already largest multi-science Grid infrastructure in the world and expected to greatly expand once the LHC is completed.
 National Programme for IT for England's National Health Service
 Navy/Marine Corps Intranet
 IBM 360
 The National Broadband Network, a FTTP network under construction in Australia, proposing to reach 90% of homes.

तेल एवं गैस की परियोजनाएँ 

 Gorgon gas project
 Southstream pipeline
 Athabasca Oil Sands
 Corrib Gas Project
 Hibernia
 Nord Stream
 Sakhalin-I
 Trans-Alaska Pipeline System
 Peregrino
 Jamnagar Refinery World's Largest Greenfield Refinery, India

पत्तन परियोजनाएँ 
 Punta Colonet in Baja California, Mexico
 Port of Rotterdam
 Yangshan port.
 Port of Sines, Portugal

रेलपथ एवं तीव्र आवागमन परियोजनाएँ 

 Beijing Subway, Beijing, People's Republic of China
 Athens Metro, Athens, Greece
 Bay Area Rapid Transit System, San Francisco Bay Area, California, USA
 Canada Line in Vancouver, British Columbia, Canada
 Crossrail, London, UK
 North West Metro between the CBD and Northwestern suburbs of Sydney, Australia
 Channel tunnel between France and the UK
 Delhi Metro, New Delhi, India
 Dubai Metro in Dubai
 Gautrain in Gauteng, South Africa between Johannesburg and Pretoria
 Gotthard Base Tunnel in Switzerland.
 Great Belt Fixed Link, Denmark
 Mumbai Metro, India
 High Speed 1, Ebbsfleet International, London, UK
 High-speed railway to Jerusalem, (Israel Railways), Israel
 London Underground
 Namma Metro, India
 Marmaray in Istanbul, Turkey, an express railway system connecting Europe and Asia under waters of Bosphorus.
 Qingzang railway in Qinghai and Tibet, China
 Seattle Light Rail, Seattle, USA
 Second Avenue Subway, New York City, USA
 Seikan Tunnel in Japan
 Shanghai Metro, Shanghai, People's Republic of China
 Jakarta Mass Rapid Transit, Jakarta, Indonesia
 Transcontinental railroads
 Washington Metro, Washington, D.C., USA
 Kolkata Metro, India
 Transit City, Toronto, Canada
 Taiwan High Speed Rail, Taiwan, ROC

सड़क यातायात की परियोजनाएँ 

 Bang Na Expressway, Thailand, Bang Na Expressway- World's longest bridge by one reading (most of it isn't a bridge.)
 Sunda Strait Bridge, Indonesia, Southeast-asian longest oversea bridge
 Rio-Antirio Bridge, Greece, Europe's largest cable-stayed bridge
 Rio-Niterói Bridge, Rio de Janeiro, Brazil
 Egnatia Odos, Greece
 A1 (Croatia) between Zagreb and Split, with extension being built to Dubrovnik, Croatia
 A3 motorway (Romania) between Braşov and Oradea
 A4 motorway (Romania) between Iaşi and Târgu Mureş
 Bundesautobahn 20, Germany
 Central Artery/Tunnel Project, more popularly known as the "Big Dig"), Boston, Massachusetts, USA
 National Highways Development Project, India
 Port Tunnel Dublin, Republic of Ireland
 Expressway Network of the People's Republic of China
 Fehmarn Belt bridge and its connections on land, linking Denmark and Germany
 Interstate Highway System, United States of America
 Millau Viaduct, France
 Oresund Bridge and its connections on land, like the City Tunnel, Malmö.
 Roman road system of antiquity
 Vasco da Gama Bridge, Portugal, Europe's largest bridge
 Karakoram Highway, Pakistan, Highest paved international road in the world

विज्ञान की परियोजनाएँ 

 International Space Station, multinational space station in low Earth orbit (1998-2016)
 ITER International nuclear fusion project, in France (Est. 2018)
 Large Hadron Collider 14 TeV particle accelerator, in Switzerland and France (2008)
 सुपरकंडक्टिंग सुपर कोलाइडर (Superconducting Super Collider), canceled 40 TeV particle accelerator, in Texas (1991-1993)
 मैनहट्टन परियोजना (Manhattan Project), संयुक्त राज्य अमेरिका (1945)
 अपोलो परियोजना (1960-1975)
 Soviet Moonshot, canceled moon landing program (1962-1969)
 Project Constellation, planned moon landing spacecraft and space shuttle replacement (Ongoing)
 Space Shuttle program (1972-2010)
 Buran program, canceled space shuttle program (1980-1993)
 मानव जीनोम परियोजना (Human Genome Project), - मानव के आनुवांशिक कूट (human genetic code) तैयार करने की परियोजना (वर्तमान)

नगरीय परियोजनाएँ 
 HafenCity in Hamburg, Germany
 Brasília in Brazil
 Jakarta Waterfront City, in Jakarta, Indonesia
 Satrio International Tourism and Shopping belt, in Jakarta, Indonesia
 Ciudad Universitaria in Mexico City, Mexico
 Dubailand in Dubai
 Esplanada City Center, Bucharest, Romania
 Expo 98/Park of the Nations in Lisbon, Portugal
 Iskandar Development Region in Johor, Malaysia
 Putrajaya, Malaysia
 King Abdullah Economic City, Saudi Arabia
 La Défense in Paris, France
 Liverpool One, Liverpool, England
 Lusail City, Doha, Qatar
 Moscow-City in Moscow, Russia
 New Songdo City in Incheon, South Korea
 Okhta Center in Saint Petersburg, Russia
 Pagcor City in Metro Manila, The Philippines
 Palm Islands, The World (archipelago) and Dubai Waterfront in Dubai
 Potsdamer Platz in Berlin, Germany
 Project CityCenter in Las Vegas, USA
 Victoria & Alfred Waterfront, Cape Town, South Africa
 Dublin Docklands in Dublin, Republic of Ireland

जल आधारभूत संरचना सम्बन्धी परियोजनाएँ 

 Chicago River reversing its course, Chicago
 Deep Tunnel Project, Chicago
 Delta Works, Netherlands
 East Bay Municipal Utility District in Oakland, California, USA
 Great Manmade River, Libya
 G-Cans project, Saitama, Japan
 HaMovil HaArtzi (National Water Carrier), Israel
 MOSE Project, Venice, Italy
 Zuiderzee Works, Netherlands
 New York City Water Tunnel No. 3, New York, New York
 Stormwater Management and Road Tunnel (SMART), Kuala Lumpur, Malaysia
 Snowy Mountains Scheme in New South Wales/Victoria, Australia
 South-North Water Transfer Project, China
 State Water Project, California
 Thames Tideway Scheme, London, United Kingdom
 Thames Barrier, London, United Kingdom

जलवायु एवं पर्यावरण सम्बन्धी परियोजनाएँ 
 Proposed sahara forest project
 Seawater Greenhouse
 Great Plains Shelterbelt
 Green Wall of China
 Aerially Delivered Re-forestation and Erosion Control System

इन्हें भी देखें 
 महाविज्ञान
 महासंरचना (Megastructure)
 समष्टि-इंजीनियरी (Macro-engineering)
 महापरियोजनाओं की सूची

सन्दर्भ

बाहरी कड़ियाँ 
 What is a megaproject?
 Borovoye-Biocity — megaproject of Bionic City for Kazakhstan — S. Rastorguev, M. Kudryashov, 2008

इंजीनियरी परियोजनाएँ