Ludwig I, Grand Duke of Hesse and by Rhine (14 June 1753 – 6 April 1830) was a German potentate. As Ludwig X, he was Landgrave of Hesse-Darmstadt from 1790 to 1806, when he upgraded his title to Grand Duke of Hesse as Ludwig I, and ultimately (in 1816 to Grand Duke of Hesse and by Rhine.

As Landgrave and Grand Duke, Ludwig presided over a significant increase in territory for Hesse-Darmstadt during the imperial reorganizations of 1801-1803, and after the dissolution of the Empire in 1806, including notably the Duchy of Westphalia , formerly part of the Archbishopric of Cologne. He was forced to disgorge this northern appendange to his lands, however, at the Congress of Vienna and gained in its stead the fortress city of Mainz on the Left Bank of the Rhine.

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— | width="40%" style="text-align: center;" |Grand Duke of Hesse
1806–1816 | width="30%" |Succeeded by:
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|- style="text-align: center;" | width="30%" |Preceded by:
— | width="40%" style="text-align: center;" |Grand Duke of Hesse and by Rhine
1816–1830 | width="30%" |Succeeded by:
Ludwig II