Johann Georg Ziesenis was a German – Danish portrait painter.
His father Johan Jürgen Ziesenis was a painter from Hanover who had been granted Danish citizenship in Copenhagen in 1709 and whose works included a 1739 Baptism of Christ for Copenhagen's garrison church. After drawing lessons from his father, Johann lived in Düsseldorf, where he gained further training and painted several portraits of the royal family. In 1764 he became court painter at Hanover and in 1766 he was granted 400 kroner by the Danish king "for travel and other expenses". In 1768 he was in the Netherlands, where he produced portraits of William V, his wife and family. He also worked for the courts in Brunswick and Berlin and his daughters Mrs Lampe (Maria Elisabeth) and Margaretha were also painters.

Johann Georg Ziesenis created about 260 portraits and other paintings and sketches in the course of his life, including ones of Crown Prince Frederik (1767, now at Fredensborg), Frederick II and Charlotte of Mecklenburg-Strelitz (future wife of George III of the United Kingdom). In 1764, whilst in his sixties, he painted a portrait of Hans Egede.