Joseph Campau (February 20, 1769 – May 13, 1863) was a merchant and landowner native to Detroit, considered one of the "Barons of Detroit". He belonged to the Campau family, one of the city's original settler families. At the beginning of the 19th century, he was among the wealthiest citizens in Michigan and is believed to have been the first millionaire in the state. He was an early benefactor of the University of Michigan.

Born in Detroit in 1769, Campau found success in business at an early age. He operated three trading posts and a merchant store in Detroit until the early 1800s. He held several public offices in the city and served as an officer in the Michigan Territory Militia during the War of 1812. He was known as Chemokamun ("big shot") by Chief Joshua Wawanosh and other Native American chiefs. Along with his nephew, John R. Williams, he founded the Democratic Free Press and Michigan Intelligencer, which would later become the Detroit Free Press. At the time of his death, he was the largest landowner in Michigan, holding a significant percentage of the stock in both the Michigan Central Railroad and the Bank of Michigan.

Campau was a somewhat controversial figure; contemporary publications labeled him a slumlord. He died in 1863 and was buried in Elmwood Cemetery rather than the traditional Catholic burial site at Mount Elliott Cemetery, as he had been excommunicated from the Catholic Church in 1817 following heated disagreements with Gabriel Richard, the rector of Ste. Anne.

Joseph Campau Street in Hamtramck and Detroit was named for him, and by association, Jos. Campau Historic District.

Campau was born on February 2, 1769, in Detroit. His parents were Jacques Campau and Catherine Ménard. Campau's great-grandfather, Jacques Campau (1677–1751), left Montreal and settled at Fort Pontchartrain du Détroit in 1708, one year after his brother Michel. Antoine de la Mothe Cadillac founded Fort Pontchartrain du Détroit in 1701 and sold 68 land grants between 1707 and 1710, two of which were sold to the Campau brothers. Jacques had previously served as a secretary and an officer to Cadillac. Jacques sold furs, grains, and bread at "one of the finest merchant stores" in Detroit by the 1740s, according to Clarence M. Burton.

In his youth, Joseph Campau traded with the Native Americans. His younger brother, Barnabé aka Barnabas, was also a wealthy businessman. He was a fur trader, merchant, and landowner. One of his properties was Belle Isle.

Campau began his business career as a merchant. He purchased goods from Boston, the first person to do so in Detroit, and sold them at his store on Atwater. Campau spoke the languages of several Native American tribes, French and English to his customers at his three trading posts at Saginaw, on Lake St. Clair, and on Lake Erie. He was called Chemokamun ("big shot") by Chief Wawanosh of Sarnia and Chief Maccounse of Lake St. Clair.

Campau was the first in the city's real estate industry to sell and lease houses that had been built on vacant lots. He was sometimes considered a "slum lord" who was likely to charge late fees with high interest rates to delinquent tenants. However, an obituary stated of Campau, "[t]o the honest and industrious, he was always lenient."