Mosynopolis (Greek: Μοσυνόπολις), of which only ruins now remain in Greek Thrace, was a city in the Roman province of Rhodope, which was known until the 9th century as Maximianopolis (Μαξιμιανούπολις) or, to distinguish it from other cities of the same name, as Maximianopolis in Rhodope.

[3] The Battle of Messinopolis, in which the Bulgarians defeated Boniface I, Marquess of Montferrat, took place nearby in 1207, and was speedily followed by the destruction of Mosynopolis by Tsar Kaloyan of Bulgaria.

[4] The fate of the town thereafter is somewhat obscure: it re-appears in 1317 as part of the theme of "Boleron and Mosynopolis", and its bishopric was still active, but the historian Catherine Asdracha, in her 1972 survey of the Rhodope area in the late Middle Ages, suggests that it never recovered from Kaloyan's sack and remained in ruins, proposing that it is to be identified with the town of Mesene, which the emperor and historian John VI Kantakouzenos reported as "destroyed many years ago".

[9][10] After the destruction of the city, the Patriarchate of Constantinople in August 1347 authorized the Metropolitan of Trajanopolis to exercise jurisdiction in what had been the see of Maximianopolis or Mosynopolis.

[12] The diocese was nominally restored in 1933 as the Latin Catholic titular archbishopric Massimianopolis in Rhodope.