border|right|300px|Constantino XI Paleólogo

'''Constantino XI Paleólogo''' (algumas vezes numerado como '''Constantino XII''' ou '''Constantino XIII'''), também conhecido como '''Constantino Drageses''' (em grego Κωνσταντίνος ΧΙ Δραγάσης Παλαιολόγος), (9 de Fevereiro de 1404 — 29 de Maio de 1453) foi o último imperador do Império Bizantino, desde 1449 até sua morte.

O reinado de Constantino XI representa a agonia do império bizantino. Esta agonia se traduziu nos revezes sofridos, tanto internamente quanto externamente. Internamente, equívocos nas relações eclesiásticas. Externamente, o ataque cada vez mais evidente dos turcos otomanos.

== Vida ==
Nascido em Constantinopla, Constantino era o oitavo dos dez filhos de Manuel II Paleólogo e Helena Dragas. Cresceu na cidade imperial sob a supervisão de seus pais e, mais tarde, assumiu oficialmente o nome de sua mãe (Drageses).

Constantino casou-se por duas vezes. A primeira vez, em primeiro de julho de 1428, com Maddelena Tocco (morta em 1429); a segunda vez, com Caterina Gattilusio (que também morreu, em 1442). Segundo algumas fontes, não houve filhos nestes casamentos; segundo outras, teria nascido uma criança chamada Magdalena.

Quando seu irmão, João VIII Paleólogo morreu, o trono foi disputado por Constantino e seu outro irmão Demetrius. Eles apelaram ao sultão Murad II para que este arbitrasse o conflito. Murad II escolheu Constantino, que foi coroado em Mistra, em 6 de janeiro de 1449. Ironicamente, seria o filho de Murad II quem, mais tarde, traria o fim do império bizantino.
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== União de Florença ==

thumb|right|250 px|Cerco de [[Constantinopla]]

Em sé romana foram admitidas pelos ortodoxos orientais. Em 1452, com a missa solene e conjunta em Constantinopla, tentou-se selar, por fim, a união. No entanto, esta cerimônia provocou uma reação contrária dos não-unionistas, que eram maioria.

== Queda de Constantinopla ==

thumb|right|Maomé II (de ''[[Gentile Bellini'')]]

{{Infobox Monarch
|name            =Constantine XI Palaiologos
|title           =Emperor of the Eastern Roman Empire
|image           =thumb|Constantine XI Palaiologos &mdash; considered a saint by the [[Eastern Orthodox Church]]
|reign           =January 6, 1449 – May 29, 1453
|coronation      =January 6, 1449
|predecessor     =John VIII Palaiologos
|successor       =None (Ottoman rule)
|spouse 1        =Maddalena Tocco<br />Caterina Gattilusio
|issue           =None
|dynasty         =|Palaiologos]] dynasty
|father          =Manuel II Palaiologos
|mother          =Helena Dragaš
|date of birth   =February 8, 1405
|date of death   =May 29, 1453
|}}

'''Constantine XI Palaiologos''' or '''Palaeologus''' (Greek: Κωνσταντίνος ΙΑ' Δραγάσης Παλαιολόγος, ''Kōnstantinos XI Dragasēs Palaiologos'', Serbian: Константин XI Палеолог Драгаш, ''Konstantin XI Paleolog Dragaš'', Palaiologos dynasty, he ruled the Byzantine Empire from 1449 to his death.

==Early life==
Constantine was born in Helena Dragaš, the daughter of the Serbian prince Constantine Dragaš of older brother in Italy, Constantine was regent in Constantinople from 1437-1440.

==Despot at Morea==
Constantine became the Despotes of Morea (the Medieval name for the Peloponnesus) in October 1443, ruling from the fortress and palace in Mistra. At the time, Mistra was a center of arts and culture rivaling Constantinople.  

After establishing himself as the Despot, Constantine worked to strengthen the defense of Morea, including reconstructing a wall across the Isthmus of Corinth called the Hexamilion, "the Six Mile Wall."  

In the summer of 1444, he launched an invasion of the Latin Florentine duke to pay him tribute. The Duchy was ruled by Nerio II Acciajuoli, a vassal of the Ottoman Sultan.  

However, his triumph was short-lived.  In the fall of 1446, the Ottomans advanced on Morea with 50-60,000 soldiers. Constantine and his brother Thomas braced for the attack at the Hexamilion, which the Ottoman army reached on November 27, 1446.  While the wall may have held against medieval attacks, Sultan Murad had cannons to supplement the usual siege engines and scaling ladders, leaving the Hexamilion in ruins by December 10.  Constantine and Thomas barely escaped.  The winter prevented a full conquest of Morea, and Murad left that to another day, but put an end to Constantine's attempt to expand his Despotate.

==Marriages==

Constantine XI married twice: the first time on Epirus, who died in November 1429; the second time to Caterina Gattilusio, daughter of Dorino of Lesbos, who also died (1442). He had no children by either marriage.

==Reign as emperor==
Despite the foreign and domestic difficulties during his reign, which culminated in the fall of Constantinople and of the Byzantine Empire, contemporary sources generally speak respectfully of the emperor Constantine. 

When his brother, Emperor Ottoman Sultan Murad II to arbitrate the disagreement.  

Murad chose Constantine, who was crowned at Maria Branković, the widow of Murad II, but the courtship failed.  

Sultan Murad died in 1451, succeeded by his 19 year old son Mehmed II. Soon afterwards, Mehmed II began agitating for ownership of Constantinople.  Constantine threatened to release Prince Orhan, a pretender to the Ottoman throne, unless Mehmed doubled an annual payment. To Mehmed, this was the last straw, and he considered Constantine to have broken the truce.  The following winter of 1451-52, Mehmed built Rumelihisari, a fortress on a hill at the European side of the Bosporus, just north of the city, as a prelude for a siege. 

Desperate for any type of military assistance, Constantine XI appealed to the West and reaffirmed the union of Eastern and Roman Churches which had been signed at the Loukas Notaras, his chief minister and military commander. Although some troops did arrive from the mercantile city states in the north of Italy, the Western contribution was not adequate to counterbalance Ottoman strength.  While Constantine also sought assistance from his brothers in Morea, any help was forestalled by an Ottoman invasion of the peninsula in 1452. The siege of the city began in the winter of 1453.

==Fall of Constantinople==
Before the beginning of the siege, Mehmed II made an offer to Constantine XI. In exchange for the surrender of Constantinople, the emperor's life would be spared and he would continue to rule in Mistra. Constantine refused this offer. 

Instead he led the defence of the city and took an active part in the fighting along the land walls. At the same time, he used his diplomatic skills to maintain the necessary unity between the Genovese, Venetian, and Greek troops. 