The Silk Route leads to Osaka; this route was used as the gateway to ancient Japan. Around the 5th century A.D., Asian continental culture came to Japan via the Korean peninsula, and Osaka was converted in a center of politics and culture in Japan. The first capital of Japan was established in Osaka in the 7th century. Around the end of the 12 century, the warrior class got the political power and the civil war started in all Japan. However, in Sakai City in the Southern area of modern Osaka Prefecture, a golden age started. Sakai received great affluence as an international port due to the Japanese naval missions to China from the area. The art of the Japanese tea ceremony was perfected in Sakai.

Osaka was previously called as Naniwa. Before the Nara period, when the capital used to be moved with the reign of each new emperor, Naniwa was once Japan's capital city, the first one ever known.

In the 16th century, Osaka was chosen as the ideal site for Toyotomi Hideyoshi's castle, and Osaka may have been Japan's capital if Tokugawa Ieyasu had not terminated the Toyotomi lineage after Hideyoshi's death and moved his government to distant Edo (Tokyo).