“Japan World Exposition Osaka 1970” was held on a 330-hectare site in Osaka Prefecture, Japan, from March 15 to September 13, 1970. Organized by the Government of Japan, it was a general exhibition of the first category under the 1928 Paris Convention. Over 183 days it recorded 64,218,770 visits, and it was the first Expo held in Japan and in Asia.

The General Assembly of the International Exhibitions Bureau (Bureau International des Expositions, BIE) registered the Expo on May 11, 1966. For Japan, the event carried a long history: the country had planned an international exposition for Tokyo in 1940 that was never held, and ticket holders for that cancelled event were allowed to enter in 1970. Historian Mayuko Sano of Kyoto University has linked the Expo to Japan's postwar economic growth and its entry into the group of advanced nations.

The theme, "Progress and Harmony for Mankind," asked how technological progress could serve a more harmonious human future. The Expo's emblem was designed by graphic designer Takeshi Otaka. The timing also mattered: the 1960s and 1970s saw many newly independent nations, which widened the pool of potential participants.

Architect Kenzō Tange served as the main planner, building on an original proposal by Uzō Nishiyama. Both were associated with the Metabolist movement, which imagined cities as adaptable, growing organisms. At the center of the plan lay the Symbol Zone, an axis 1 kilometer long and 150 meters wide that held the Festival Plaza, the Theme Pavilion, the Tower of the Sun, and the Expo Tower. Tange's Festival Plaza was covered by "the big roof," a double-layer space frame of steel tubes measuring 108 by 297 meters and set 30 meters above the ground. It was clad in transparent pneumatic plastic panels and raised into place with pneumatic jacks, a novel technique at the time, and experimental capsules attached to it presented alternative visions of urban living.

Artist Tarō Okamoto's Tower of the Sun rose 70 meters through an opening in the big roof. Built as part of the Theme Pavilion, it housed the Tree of Life, a 41-meter structure carrying 292 models of living organisms. Exhibition sections underground, at ground level, and in the air around it represented the past, the present and the future.

Seventy-seven countries took part, and the site held 116 pavilions built by governments, international organizations, states and provinces, cities and companies. The Japan Pavilion, laid out in the shape of a cherry blossom, covered 37,791 square meters. The United States presented a pavilion with an air-supported cable roof and displayed a lunar module along with rocks returned by Apollo 12. Brazil's pavilion, with its concrete roof by Paulo Mendes da Rocha, became an icon of Brutalist architecture. Switzerland built a branching metal "Radiant Structure," Australia's pavilion by James MacCormick hung its circular roof from a suspension structure, and the Netherlands offered a multimedia pavilion.

Corporate pavilions introduced technologies that later entered daily life. The Fuji Group Pavilion, an air-inflated membrane structure, presented the first IMAX film, “Tiger Child.” The NTT pavilion demonstrated "The Dream Telephone," an early public showing of mobile telephony, and the Sanyo Pavilion displayed an "Ultrasonic Bath" prototype. Kishō Kurokawa's Takara Beautillion, built from modular units, inspired the world's first capsule hotel.

Crowds were immense. The busiest day, September 5, 1970, brought 836,000 visits, and the Expo's total attendance remained the highest in Expo history until Expo 2010 Shanghai. Preparing the region for these numbers spurred urban development, including about 110 kilometers of new roads.

After the Expo closed, the Festival Plaza's big roof was dismantled and the grounds became the Expo '70 Commemorative Park, which covers about 260 hectares and keeps a part of the original facilities, including the Japanese Garden. The Tower of the Sun still stands at its center. Its interior reopened as a museum in 2018. In 2020 the tower was registered as a Tangible Cultural Property of Japan, and on August 27, 2025, it was designated an Important Cultural Property. When Osaka hosted Expo 2025 Osaka, trees from the 1970 site were transplanted to that Expo's Forest of Tranquility.

Expo 1970 Osaka marked Japan's arrival as a host of Expos and gave a generation of Japanese architects, artists and designers an international stage. Its blend of Metabolist planning, bold engineering, and mass participation shaped how later Expos imagined the city of the future.