Jiangsu borders Shandong in the north, Anhui to the west, and Zhejiang and Shanghai to the south. Jiangsu has a coastline of over one thousand kilometers along the Yellow Sea, and the Yangtze River passes through its southern parts. Since the inception of economic reforms in 1978, Jiangsu has been a hot spot for economic development, and is now one of China's most prosperous provinces. The wealth divide between the rich southern regions and the north, however, remains a prominent issue in the province.

During the earliest Chinese dynasties, the area in what is now Jiangsu was far removed from the center of Chinese civilization, which was in the northwest Henan; it was home of the Huai Yi, an ancient ethnic group. During the Zhou Dynasty more contact was made, and eventually the state of Wu (centered at Gusu, now Suzhou) appeared as a vassal to the Zhou Dynasty in south Jiangsu, one of the many hundreds of states that existed across northern and central China at that time. Near the end of the Spring and Autumn Period, Wu became a great power under King Helu of Wu, and was able to defeat in 484 BC the state of Qi, a major power in the north in modern-day Shandong province, and contest for the position of overlord over all states of China. The state of Wu was subjugated in 473 BC by the state of Yue, another state that had emerged to the south in modern-day Zhejiang province. Yue was in turn subjugated by the powerful state of Chu from the west in 333 BC. Eventually the state of Qin swept away all the other states, and established China as a unified nation in 221 BC.

Under the reign of the Han Dynasty (206 BC to 220 AD), which brought China to its first golden age, Jiangsu was a relative backwater, far removed from the centers of civilization in the North China Plain. Jiangsu was at that time administered under two zhou (provinces): Xuzhou Province in the north, and Yangzhou Province in the south. Although south Jiangsu was eventually the base for the kingdom of Wu (one of the Three Kingdoms from 222 to 280), it did not become significant role until the invasion of northern nomads during the Western Jin Dynasty, starting from the fourth century. As northern nomadic groups established kingdoms across the north, ethnic Han Chinese aristocracy fled southwards and set up a refugee Eastern Jin Dynasty in 317, in Jiankang (modern day Nanjing). From then until 581 (a period known as the Southern and Northern Dynasties), Nanjing in south Jiangsu was the base of four more ethnic Han Chinese dynasties facing off with northern barbarian (but increasingly sinicized) dynasties. In the meantime, north Jiangsu was a buffer of sorts between north and south; it initially started as a part of southern dynasties, but as northern dynasties gained more ground, it became part of northern dynasties.

In 581 unity was reestablished again, and under the Tang Dynasty (618 to 907) China once more went through a golden age, though Jiangsu at this point was still rather unremarkable among the different parts of China. It was during the Song Dynasty (960-1279), which saw the development of a wealthy mercantile class and emergent market economy in China, that south Jiangsu emerged as a center of trade. From then onwards, south Jiangsu, especially major cities like Suzhou or Yangzhou, would be synonymous with opulence and luxury in China. Today south Jiangsu remains one of the richest parts of China, and Shanghai, arguably the wealthiest and most cosmopolitan of mainland China cities, is a direct extension of south Jiangsu culture.

The Beisi Pagoda of Suzhou, built between 1131 and 1162 during the Song Dynasty (with later renovations), 76 m (243 ft) tall.The Jurchen Jin Dynasty gained control of North China in 1127, and the river Huai He, which used to cut through north Jiangsu to reach the Yellow Sea, was the border between the north, under the Jin, and the south, under the Southern Song Dynasty. The Mongols took control of China in the thirteenth century. The Ming Dynasty, which was established in 1368 after driving out the Mongols who had occupied China, initially put its capital in Nanjing. Following a coup by Zhu Di (later Yongle Emperor), however, the capital was moved to Beijing, far to the north. (The naming of the two cities continue to reflect this: "Nanjing" literally means "southern capital", "Beijing" literally means "northern capital.) The entirety of modern day Jiangsu as well as neighbouring Anhui province kept their special status, however, as territory-governed directly by the central government, and were called Nanzhili ("Southern directly-governed"). Meanwhile, South Jiangsu continued to be an important center of trade in China; some historians see in the flourishing textiles industry at the time incipient industrialization and capitalism, a trend that was however aborted, several centuries before similar trends took hold in the West.