Suzhou is a major prefecture-level city in southern Jiangsu province, China. It is part of the Yangtze Delta megalopolis.

Founded in 514 BC, Suzhou rapidly grew in size by the Eastern Han dynasty, mostly due to emigration from northern China. From the 10th century onwards, it has been an important economic, cultural, and commercial center, as well as the largest non-capital city in the world, until it was overtaken by Shanghai in approximately 1850. Since economic reforms began in 1978, Suzhou attained GDP growth rates of about 14% in 35 years. In 2023, Suzhou had 5 million registered residents. Suzhou is listed as the # 42 cities by scientific output according to the Nature Index 2024. The city is home to universities, including Soochow University, Suzhou University of Science and Technology, Xi'an Jiaotong–Liverpool University, and Changshu Institute of Technology.

The city's tourist attractions include canals, stone bridges, pagodas, and gardens. Along with Hangzhou, it is sometimes described as heaven on earth. The Classical Gardens of Suzhou were added to the list of the UNESCO World Heritage Sites in 1997 and 2000.

During the Zhou dynasty, a settlement known as Gusu after nearby Mount Gusu (Chinese: 姑苏山; pinyin: Gūsūshān) became the capital of the state of Wu. From this role, it also came to be called Wu as well. In 514 BC, King Helü of Wu established a new capital nearby at Helü City and this grew into the modern city. During the Warring States period, Helü City continued to serve as the local seat of government. From the areas it administered, it became known as Wuxian (lit. "Wu County") and Wujun ("Wu Commandery"). Under the Qin, it was known as Kuaiji after its greatly enlarged commandery, which was named for the reputed resting place of Yu the Great near modern Shaoxing in Zhejiang.

The name "Suzhou" was first officially used for the city in AD 589 during the Sui dynasty. Su (蘇 or 苏) in its name is a contraction of the old name Gusu. It refers to "Satisfied place" in the Old Yue language. The zhou 州 originally meant something like a province or county (cf. Guizhou), but often came to be used metonymously for the capital of such a region (cf. Guangzhou, Hangzhou, etc.). Suzhou is the Hanyu Pinyin spelling of the Putonghua pronunciation of the name. Prior to the adoption of pinyin, it was variously romanized as Soo-chow, Suchow, or Su-chow.

Suzhou, the cradle of Wu culture, is one of the oldest towns in the Yangtze Basin. By the Spring and Autumn period of the Zhou, local Baiyue tribes named the Gou Wu are recorded living in the area which would become the modern city of Suzhou. These tribes formed villages on the edges of the hills above the wetlands surrounding Lake Tai.

Sima Qian's Records of the Grand Historian records traditional accounts that the Zhou lord Taibo established the state of Wu at nearby Wuxi during the 11th century BC, civilizing the local people and improving their agriculture and mastery of irrigation. The Wu court later moved to Gusu within the area of modern Suzhou. In 514 BC, King Helü of Wu relocated his court nearby and called the settlement Helü City after himself. His minister Wu Zixu was closely involved with its planning and it was this site that grew into present-day Suzhou. The height of his tower on Gusu Hill (Gusutai) passed into Chinese legend. In 496 BC, King Helü was buried at Tiger Hill. In 473 BC, Wu was defeated and annexed by Yue, a kingdom to its southeast; Yue was annexed in turn by Chu in 306 BC. Remnants of the ancient kingdom include pieces of its 2,500-year-old city wall and the gate through it at Pan Gate.

The city was originally laid out according to a symbolic three-by-three grid of nine squares, with the royal palace occupying the central position.