<Tr> <Th> Residence </Th> <Td> Grand Ducal Palace in Luxembourg </Td> </Tr> <Tr> <Th> Website </Th> <Td> Monarchie.lu (in French) </Td> </Tr> <P> The Grand Duke of Luxembourg is the monarchical head of state of Luxembourg . Luxembourg has been a grand duchy since 15 March 1815, when it was elevated from a duchy, and was in personal union with the United Kingdom of the Netherlands until 1890 under the House of Orange - Nassau and is the world's only sovereign grand duchy . Since 1815, there have been nine monarchs of Luxembourg, including the incumbent, Henri . </P> <P> The constitution of Luxembourg defines the grand duke's position: </P>

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