Oudenaarde (Dutch pronunciation: [ˈʌudənaːrdə] ⓘ; French: Audenarde [odnaʁd]; in English sometimes Oudenarde) is a Belgian city and municipality in the Flemish province of East Flanders.

The municipality comprises the city of Oudenaarde proper and the towns of Bevere, Edelare, Eine, Ename, Heurne, Leupegem, Mater, Melden, Mullem, Nederename, Volkegem, Welden and a part of Ooike.

The town's name, meaning "old field", still lingers on in "outnal", an obsolete English term for a kind of brown linen thread.

The history of the current municipality of Oudenaarde starts in 974, when Otto II, Holy Roman Emperor and king of Germany, built one of its three fortifications on the Scheldt at Ename to protect his kingdom against possible attacks from Francia (next to the other frontier post at Valenciennes, later in also the Margraviate of Antwerp).

By that time, the former merchants and guild artisans of Ename easily got across the Scheldt to the recently founded city of Oudenaarde.

Throughout the Middle Ages, the city was one of the staunchest supporters of the counts of Flanders, defending them against insurrections from the South, and even from Ghent.

During the Reformation, the people of Oudenaarde chose Protestantism and allied themselves with Ghent against Charles V. In 1582, after a prolonged siege by Margaret's son, Alexander Farnese, the city finally gave in, causing most merchants, workers, and even nobles to flee.

The men's Tour of Flanders has passed through Oudenaarde on several occasions, finishing in the town since 2012, and it regularly ascends the Koppenberg hill in the municipality.