What is Constantine I of Greece?
{{Infobox royalty |name = Constantine I |image = file:Constantineiofgreece.jpg |caption = Constantine in 1921 |succession = [[King of the Hellenes]] |reign = {{nowrap|18 March 1913 – 11 June 1917}} |reign-type = First reign |predecessor = [[George I of Greece|George I]] |successor = [[Alexander of Greece|Alexander]] |reg-type = {{nowrap|Prime Ministers}} |regent = {{list collapsed|title=''See list''|1=[[Eleftherios Venizelos]]<br />[[Dimitrios Gounaris]]<br />[[Alexandros Zaimis]]<br />[[Stephanos Skouloudis]]<br />[[Alexandros Zaimis]]<br />[[Nikolaos Kalogeropoulos]]<br />[[Spyridon Lambros]]}} |reign-type1 = {{nowrap|Second reign}} |reign1 = 19 December 1920 – {{nowrap|27 September 1922}} |predecessor1 = [[Alexander of Greece|Alexander]] |successor1 = [[George II of Greece|George II]] |reg-type1 = Prime Ministers |regent1 = {{List collapsed|title=''See list''|1=[[Nikolaos Stratos]]<br />[[Petros Protopapadakis]]<br />[[Nikolaos Triantafyllakos]]}} |birth_date = {{Birth date|df=yes|1868|8|2}} |birth_place = [[Athens]], [[Kingdom of Greece]] |death_date = {{Death date and age|df=yes|1923|1|11|1868|8|2}} |death_place = [[Palermo]], [[Kingdom of Italy]] |burial_date = 14 January 1923 |burial_place = [[Naples]], [[Italy]] <br/> 22 November 1936 <br/>Royal Cemetery, [[Tatoi Palace]], [[Greece]] |spouse = {{marriage|[[Sophia of Prussia]]|27 October 1889}} |issue = {{plainlist| * [[George II of Greece]] * [[Alexander of Greece]] * [[Queen Helen, Queen Mother of Romania]] * [[Paul of Greece]] * [[Princess Irene, Duchess of Aosta]] * [[Princess Katherine of Greece and Denmark|Princess Katherine]]}} |house = [[House of Glücksburg|Glücksburg]] |father = [[George I of Greece]] |mother = [[Olga Constantinovna of Russia]] |religion = [[Greek Orthodox]] }} '''Constantine I''' ({{lang-el|Κωνσταντίνος Αʹ}}, ''Konstantínos I''; {{OldStyleDate|2 August|1868|21 July}} – 11 January 1923) was [[King of Greece]] from 18 March 1913