List of fictional monarchs of real nations

This is a list of fictional monarchs – characters who appear in fiction as the monarchs (kings, queens, emperors, empresses, etc.) of real countries. They are listed by country, then according to the production or story in which they appeared.
U.
The United Kingdom, England, Scotland and Ireland.
Books by John Whitbourn.
John Whitbourn had written several books set in a 'Catholic universe'.
"The Emberverse" series by S. M. Stirling.
In the apocalyptic series that begins with "Dies the Fire", some of the British Royal Family are evacuated to the Isle of Wight.
"Infinite Worlds".
In the "GURPS" role-playing game "Infinite Worlds", in the year 1120 the "White Ship" carrying William the Aetheling, the heir of Henry I of England, did not hit a rock in the English Channel. William survived the voyage and eventually assumed the throne - becoming known as William III of England. Neither the Empress Matilda nor Stephen of Blois had any claim on the throne. William's descendants constituted more than seven centuries of English monarchs, with the House of Plantagenet retaining unbroken power. Ultimately the "Anglo-French Empire" became a world-spanning power, achieving an Industrial Revolution much earlier. However, in 1902 unknown parties detonated a nuclear device, destroying the royal family.
"The Moon Maid" and "Moon Men" by Edgar Rice Burroughs.
Published in the early 1920s, "The Moon Maid" and "The Moon Men" envisioned a twentieth century in which "The Great War" would have gone on uninterrupted, though with varying intensity, from 1914 and until 1967 – ending with the total victory of the Anglo-Saxon Powers, Britain and the US, and the complete defeat and surrender of all other powers. Britain and the US thereupon become co-rulers of the planet, London and Washington being the twin planetary capitals and the US President and British Monarch acting as co-rulers, and with the British-American domination of the world imposed by the International Peace Fleet, made up of airships. In the first decades of the 21st century, the world basks in peace, there seems no enemy and no threat anywhere, and pressure grows for complete disarmament and scrapping of the International Peace Fleet. It is the (unnamed) King of Britain who strongly resists this pressure, and due to him half of the Fleet and of the world's armament industries are retained. This is not enough to resist the invasion fleet of the wild Kalkars from the Moon, led by the renegade Earthman Orthis, which suddenly descends on the world in 2050, capturing London and Washington and ranging the world at will. But by the British King's foresight there was still a remnant of the Fleet in existence, which kills the renegade Orthis – facilitating humanity's eventual liberation from Kalkar domination, though only centuries later.