It was an important center of inland water transportation on Lake Biwa and was referred to in the Man'yōshū as Shiga no Ōwada (志賀の大わだ) and Shigatsu (志賀津).

[2] It was also on the main land routes, the Tōkaidō and the Nakasendō connecting the eastern provinces with the ancient capitals of Japan.

[5][2] Ōtsu prospered during the Edo period because of its port on Lake Biwa and as Ōtsu-juku, a major shukuba on the Tōkaidō and Nakasendō highways.

The city was under direct administration of the Tokugawa shogunate, both for its strategic location and for its role as a center of travel and trade.

Nicholas, returning to Kyoto after a day trip to Lake Biwa, was attacked with a saber by Tsuda Sanzō (1855 – 1891), an escort policeman.

[10][11] For a while the local populace considered renaming the city to avoid the stigma associated with the scandal, but the idea was eventually shelved.

The canal, which was later expanded during the Taishō period, played an important role in connecting the cities, facilitating water and passenger transportation, and providing electrical energy to power Japan's first streetcar railroad services.

Ōtsu is located on the southern and western shore of Lake Biwa and occupies most of the southwestern portion of Shiga Prefecture.

[15] Ōtsu has a mayor-council form of government with a directly elected mayor and a unicameral city council of 38 members, who serve a term of four years.

In terms of national politics, the city is part of Shiga 1st district of the lower house of the Diet of Japan.

Ōtsu was historically noted for the production of several products, including Ōtsu-e, a form of folk drawing purchased by travelers in the Edo period; the Ōtsu soroban, an abacus used widely in Japan from the early 17th century; Zeze-yaki and Konan-yaki, forms of ceramics produced in the Edo period; and Zeze-cha, the first Japanese tea to be exported to the United States.

[19][20][21][22] Ōtsu, while not an agricultural city, is home to the production of edible chrysanthemums, used in Japanese cuisine in tempura and decoratively on platters of sashimi.

[26][27] The JR Central Tōkaidō Shinkansen runs through areas of Ōtsu, but stops at no stations in the city.

[34] Ōtsu is home to numerous historical sites, temples, shrines, and other buildings, many of them designated as National Treasures of Japan.

The Setagawa Dam was constructed in 1961 to regulate the level of Lake Biwa, is located in the Nangō district of Ōtsu.

The sights were depicted by Hiroshige (1797 – 1858) in several different series of ukiyo-e pictures, and served as an inspiration for other artists and literary figures.

[53] The Ōtsu Matsuri is thought to have begun in the early Edo period, and the first written record of the festival dates to 1624.

Many of the hikiyama in use today date from the Edo period, and are accompanied by matsuri-bayashi festival music unique to the city.