Arend ("Aad") Koudijzer (Maassluis, 15 December 1947) is a Dutch former soccer player. The central attaquer played the most of his career in Belgium.
Koudijzer was transferred in 1968 from the amateur team VDL-Maassluis to SVV weggeplukt bij amateurvereniging VDL-Maassluis. He was the top scorer of the Dutch First Division in his first season in the professional soccer scoring 32 goals. Under the guidance of coach Rinus Gosens, he was champion with his team and promoted to the Eredivisie. One year later, he made the transfer to Sparta Rotterdam. With this team, he played in the UEFA Cup in 1970/1971 and in the Europacup II in 1971/72. He scored two times in four European games.
At Sparta, the strong header Koudijzer didn't get a starting position and often took the role of pinch-hitter. In 1972, he moved to KSV Waregem in the Belgian Second Division, in which the Dutchman Hans Croon was trainer. He was the top scorer in Second Division in the season 1972/1973 together with his fellow countryman Hans Posthumus of KRC Mechelen. Waregem promoted to First Division and won the Belgian Cup. In the final against KSK Tongeren, Koudijzer scored two goals.
In 1978, Koudijzer was contracted by AA Gent. The Buffalo's played in Second Division at that time. In 1980, the team was the champion and promoted to the First Division. KAA Gent qualified for the UEFA Cup in 1982 and 1983. 1984, the team with, next to Koudijzer, among others Cees Schapendonk and Soren Busk the Belgian Cup. After that season, Koudijzer finished his soccer career.
Koudijzer was subsequently the coach of Beerschot VAC (1984–1986), KV Courtrai (1986) and, starting in 1990 again Beerschot. In January 1991, he was fired by his latest team. He left the soccer world and became a truck driver. In 2008, he's gone on retirement.