Nicholas Eudaimonoioannes (Greek: Νικόλαος Εὺδαιμονοϊωάννης) was a senior Byzantine official of the early 15th century, most notable as ambassador to the Papacy during the Council of Constance and to the Republic of Venice on several occasions.
What this relation was is unknown, although the Greek historian Haris Kalligas has suggested that his son George may have married a daughter of Manuel II sometime shortly after 1415.
[3][6] The Byzantine envoys first visited Venice in February, where they offered to mediate for the conclusion of peace between the Venetian Republic and the King of Hungary, Sigismund, but also asked for aid in rebuilding the Hexamilion wall that protected the entrance to the Morea, and urged the formation of a Christian league against the Ottoman Empire.
[7] In April 1419 he was at Venice, apparently on a private matter, as he sought and gained permission of the Venetian Senate for the export of wood to repair a church in his native Monemvasia.
[8] He was back at Venice in January of the next year, on another diplomatic mission from the Emperor; again he discussed with the Senate the issue of peace with Sigismund, as well as matters concerning the two states.