Downham Market, sometimes simply referred to as Downham, is a market town and civil parish in Norfolk, England. It is on the edge of the Fens, on the River Great Ouse, approximately 11 miles (18 km) south of King's Lynn, 39 miles (63 km) west of Norwich, and 30 miles (48 km) north of Cambridge.

The civil parish has an area of 5.20 square kilometres (2.01 sq mi) and at the 2011 census had a population of 9,994 in 4,637 households. It now includes the hamlet of Broomhill, formerly part of Wimbotsham parish to the north of the town.

The town was an agricultural centre, developing as a market for the produce of the Fens with a bridge across the Ouse. During the Middle Ages, it was famed for its butter market and also hosted a notable horse fair. The market is now held Fridays and Saturdays.

Notable buildings in the town include its medieval parish church, dedicated to St Edmund, and the Victorian clock tower, constructed in 1878. The town is also known as the place where Charles I hid after the Battle of Naseby. In 2004 the town completed a regeneration project on the Market Place, moving the market to the town hall car park. The decorative town sign depicts the crown and arrows of St Edmund with horses to show the importance of the horse fairs in the town's history. A heritage centre, Discover Downham, opened in a former fire station in 2016. The town is twinned with Civray, Vienne, France.

The towns name means 'Hill homestead/village' with a market. The town is situated on a terrace overlooking the Great Ouse.

For the purposes of local government, the parish falls within the district of King's Lynn and West Norfolk. The Norfolk County Council electoral division of Downham Market covers a lesser area than that of the parish; the population of this division taken at the 2011 Census was 7,988. In February 2022, eight town councillors, including the mayor Jenny Groom, resigned over claims of bullying. The town is part of South West Norfolk parliamentary constituency.

Historically, Downham Market was an important market centre for the surrounding agricultural area. It incorporated a famous horse fair and weekly livestock and butter markets. There were several maltings in the town supplying the brewing trade in the town at a time when beer was often safer to drink than well water.

Before the arrival of the railway in 1846, the riverside was largely agricultural with warehousing for river transport centred on the Great Ouse at Downham West. With the coming of the railway, there was a rapid industrial and residential development into Downham Market.