| Wilhelm I of Katzenelnbogen | |
| Father: | Diether V of Katzenelnbogen |
| Mother: | Margaret of Jülich |
| Spouse: | Imgard (Jutte) of Isenberg-Büdingen Adelheid of Waldeck |
| Birth Date: | 1270/71 |
| Death Date: | 18 November 1331 |
Wilhelm I, Count of Katzenelnbogen (1270/71 - 18 November 1331) was a Count from the elder line of the House of Katzenelnbogen. He ruled Lower Katzenelnbogen from 1276 to 1331. Wilhelm was the son of Diether V of Katzenelnbogen (died 1276) and Margaret of Jülich (died 1292), daughter of William IV of Jülich.[1]
In 1301, Wilhelm allied himself with the four Rhenish Electors who were demanding excessive customs duties for shipping on the Rhine river. King Albert I sought to eliminate these duties which led to a war in which the King, aided by the Imperial Cities, defeated the Rhenish Electors. Having allied himself to the losing side of this war, Wilhelm lost part of his territory as a consequence.
In 1319, the Archbishop of Trier granted Wilhelm the right to build Reichenberg Castle, to quell feuds in the area and also to fortify the core area of Katzenelnbogen with its possessions on the Rhine. The castle was still under construction at the time of Wilhelm's death. Construction was completed during the reign of Wilhelm's son Wilhelm II although the latter was less enthusiastic about the project.[2]
Prior to his death, Wilhelm established a Majorat, under which the eldest son was the sole successor and the county could not be further subdivided as had been done by his grandfather, Diether IV (died 1245), who divided Katzenelnbogen into Lower and Upper counties so that his two sons could each inherit. After Wilhelm's death in 1331, the Lower county passed to his son Wilhelm II who died in 1385 with no issue and then to Wilhelm II's brother Eberhard V. When Eberhard V died in 1402, the Lower county passed to his only daughter Anna, who was married to Johann IV from the younger line, which resulted in the reunification of the two counties.
Wilhelm died on 18 November 1331 and was buried at Eberbach Abbey, which had been established as the burial place for the Counts of Katzenelnbogen by his uncle Eberhard I. Wilhelm's tomb was located in 1612/14 in the monastery church in front of the altar of St. John. The burial slab was later mounted on the wall during a reconstruction. Portions of the burial slab are now on display in the Abbey Museum.[2]
Wilhelm was married twice.:[1] In 1284 he married Imgard (Jutte) of Isenberg-Büdingen (died 1309), daughter of Louis I. They had two children[1]
Wilhelm then married 23 January 1314 to Adelheid of Waldeck (1290 - 1 September 1329, buried in the tomb at the collegiate church of St. Goar), daughter of Otto I, Count of Waldeck. Their children were:[1]