Konstantin Pavlovich, grand duke of Russia and the son of Emperor Paul I of Russia (born 1779)

Konstantin Pavlovich was a grand duke of Russia and the second son of Emperor Paul I and Sophie Dorothea of Württemberg. He was the heir-presumptive for most of his elder brother Alexander I's reign, but had secretly renounced his claim to the throne in 1823. For 25 days after the death of Alexander I, from 19 November (O.S.)/1 December 1825 to 14 December (O.S.)/26 December 1825 he was known as His Imperial Majesty Konstantin I Emperor and Sovereign of Russia, although he never reigned and never acceded to the throne. His younger brother Nicholas became tsar in 1825. The succession controversy became the pretext of the Decembrist revolt.

Grand duke is a European hereditary title, used either by certain monarchs or by members of certain monarchs' families. The title is used in some current and former independent monarchies in Europe, particularly:

• in present-day Luxembourg, the last surviving Grand Duchy
• historically by the sovereigns of former independent countries, such as Tuscany
• in Baden, Hesse, Oldenburg, Mecklenburg-Schwerin, Mecklenburg-Strelitz and Saxe-Weimar-Eisenach – grand duchies from 1815 to 1918, and all now part of Germany
• formerly also in some countries in Northern Europe, such as the Grand Duchy of Finland or the Grand Duchy of Lithuania
• currently by claimants to the Russian Imperial Throne

Paul I was Emperor of Russia from 1796 until his assassination in 1801.

June 27 is the 178th day of the year in the Gregorian calendar; 187 days remain until the end of the year.