Ahlen (German pronunciation: [ˈaːlən] ^ⓘ; Westphalian: Aulen) is a town in North Rhine-Westphalia, Germany, 30 km southeast of Münster. Ahlen is part of the District of Warendorf and is economically the most important town in that district.^{[citation needed]} Ahlen is part of the larger Münster region, and of the historic Münsterland area. The nearby villages of Dolberg, Vorhelm and Tönnishäuschen are part of Ahlen, as well. The largest neighboring town is the city of Hamm to the southwest.

Surrounding Ahlen are the towns of Sendenhorst, Ennigerloh, Beckum, Lippetal, Heessen (District of the city of Hamm) and Drensteinfurt.

The first recorded mention of Ahlen is in the Vita Liudgeri, dating to about the year 850. The reason for the name, which means "eels", are unknown. An eel bedecked with a crown and feathers is on the town's coat of arms.

The start of settlement was likely due to there being a crossing over the river Werse, which was also the crossing of two key roads (Hamm–Ahlen–Warendorf and Beckum–Ahlen–Herbern), and the beginning of a third road (Ahlen–Münster). In its early centuries, the fledgling settlement was built around an episcopal court. Within the safe haven of this church fortification, the first settlers were craftsmen and merchants who traded with the local farmers and peasants of the court. Long-distance trading started in the second half of the 12th century — proof being the names of Ahlen merchants found on invoices from merchants in Lübeck. Ahlen was also part of the north German Hanse. During this time a town wall with five towers was built (about 1271). The stripping away of the town wall had begun in the year 1765 and the last hint of it was gone by 1929.

Ahlen grew quickly during the 13th century and in or about the year 1285, the population was so high that a new church (St. Marien) was founded next to the old one (St. Bartholomäus). This leads to the likelihood that Ahlen was one of the 18 biggest towns in Westphalia, at that time. However, the town's growth was hindered in the 14th century by the Black Death. According to the town's census book of 1389, only 63 families were left in Ahlen. But the town rebounded. In 1454, a citizen list showed 212 families living in Ahlen; seven noble families and their attendants lived in the episcopal court as well. Based on this number of families, a calculated population estimate of 1,300 citizens would be realistic. By this time the town had four quarters — all of which being about the same size and each quarter being named after its own town gate. Each quarter was responsible for defending its part of the town wall and gate.

During the 16th century, there were three plague epidemics in 1505, 1551 and 1592; leprosy also killed many people. In the year 1571, the mayor and the council decided to build a special hospital for leprosy. Disastrous fires in 1483, 1668 and 1744 were responsible for further halting Ahlen's growth.

About 20 documents of witch trials during the time from 1574 until 1652 survive. The hunt for witches started in 1574 with the death of four women. Thereafter, Peter Kleikamp was charged with being a werewolf; he was tortured and burned alive on the pyre. In 1616, Christian zum Loe was charged with wizardry; he went insane and died while in jail. The last known case was in 1652 against Anna Sadelers; she was tortured, burned alive on the pyre and beheaded.

In 1938 the people of Ahlen destroyed the Ahlen synagogue. By November 1938, there were no more Jews in Ahlen.