Avenue Guillaume, named after Grand Duke William IV.
'Guillaume' is French for William. William IV reigned from 1905 until his death in 1912. The father of six daughters, in 1907 he made the eldest, Marie-Adélaïde, heir to the throne; she and then her sister Charlotte reigned after him. During the German occupation (1940–1944) the avenue was called 'Wilhelmallee'.