Fritzlar (German pronunciation: [ˈfʁɪtslaːɐ̯] ^ⓘ) is a small town (pop. 15,000) in the Schwalm-Eder district in northern Hesse, Germany, 160 km (99 mi) north of Frankfurt, with a storied history.

The town has a medieval center ringed by a wall with numerous watch towers. thirty-eight meters (125 feet) high, the "Grey Tower" ("Grauer Turm") is the highest remaining urban defense tower in Germany. The city hall, first documented in 1109, with a stone relief of St. Martin, the town's patron saint, is the oldest in Germany still in use for its original purpose. The Gothic church of the old Franciscan monastery is today the Protestant parish church, and the monastery's other buildings have been converted into a modern hospital. Many houses in the town center, notably around the market square, date from the 15th to 17th centuries and have been carefully maintained or restored. The town is dominated by the imposing Romanesque-Gothic Church of St. Peter from the 12th-14th centuries.

In 1974, the town hosted the 14th Hessentag state festival.

Fritzlar lies in northern Hesse, mainly on the north bank of the Eder river. Ten villages in the surrounding area were incorporated into the town in 1974, among them the former town of Züschen. The area is characterized by fertile farmland and mostly wooded basalt peaks, many of which are topped by mediaeval castles or castle ruins. Examples of these can be found at Gudensberg, Homberg, Felsberg, Heiligenberg, Altenburg, Jesberg, and Naumburg, among others.

The Anglo-Saxon missionary Saint Boniface, apostle of the Germans, established a church and monastery dedicated to Saint Peter in Fritzlar in 724. The current Saint Peter's Church, constructed in the 11th century, is accompanied by a monument to Boniface.

Boniface also established the first bishopric in Germany outside the boundaries of the old Roman Empire on a hill (Büraburg) across the Eder river, where a Frankish fortress and town provided protection, but after the death of Witta, its first and only bishop, in 747 the bishopric was incorporated into the diocese (later archdiocese) of Mainz by Lullus, the disciple and successor of Boniface as archbishop of Mainz. The Benedictine monastery founded by Boniface in Fritzlar in 724 gained prominence as a center of religious and worldly learning under its first abbot, Saint Wigbert, who built the original stone basilica of 732 on the site of Boniface's wooden chapel. In 782 emperor Charlemagne granted it imperial protection and substantial territory, and this triggered the rapid development of the town around it. The monastery was converted into a college of secular canons (Chorherrenstift) in 1005, its members no longer living in monastic union and simplicity, but maintaining their own, and generally rather well-to-do, households in town in the vicinity of the church. Several imposing stone residences (Curias) built by wealthy canons during the 14th century survive to this day in the old part of the town. The canons' college was dissolved only in 1803.

Located at the crossroads of several important trade routes and site of an imperial residence since Charlemagne, Fritzlar was a frequent site of royal visits and of assemblies and synods of the German princes and church leaders during the early Middle Ages. Undoubtedly the most important of these was the Reichstag of 919 when Henry I ("Henry the Fowler"), duke of Saxony, was elected King of the Germans to succeed Charlemagne's Frankish successors on the throne of what had become known as the East Frankish Empire. This event marked the end of bitter rivalry between the two large German tribes of the Franks and the Saxons and the beginning of the German Empire that lasted until the Napoleonic wars. King Conrad I of Germany, duke of Franconia, had died in December 918 without a son and urged his brother, margrave Eberhard, who was to succeed him as Duke of Franconia, to nominate Henry as king, although they had been at odds with each other from 912 to 915 over the title to lands in Thuringia. Conrad's choice was respected by the Reichstag of 919, where Henry was proclaimed king by the leaders of the Franks and Saxons. Burchard I, Duke of Swabia quickly swore allegiance as well, but Duke Arnulf of Bavaria did not submit to Henry until the latter advanced with an army into Bavaria in 921.

Conrad himself had risen to the position of duke of Franconia only after defeating the rival Babenberg counts in a battle near Fritzlar in 906, in which his father, Conrad, Duke of Thuringia the Elder, was killed.